Mammalian Physiology Midterm 2 (ch 6-11)

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Human Physiology
Chapters 6-11
updated 9 years ago by srigot55
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1

Interneurons

• Completely within CNS
• Complex branching that allows for communication with other neurons
• Can be very small
• afferent

2

efferent neurons

•somatic motor and autonomic neurons
 Somatic motor division- controls skeletal muscles
 Autonomic division- controls smooth and cardiac muscles, exocrine glands, some endocrine glands, and some types of adipose tissue
• Enlarged axon terminals

3

synapses

the region where an axon terminal communicates with its postsynaptic target cell
 presynaptic cell- the neuron that delivers a signal to the synapse
 postsynaptic cell- the cell that receives the signal
 synaptic cleft- gap between presynaptic cell and postsynaptic cell that is filled with extracellular matrix whose fibers hold the cells in position

 Graded potential -> action potential -> synapse (axon terminal)

4

neural development

 use chemical signals to find target (growth factor, molecules in the extracellular matrix, membrane proteins along growth cones)
 the axons of embryonic nerve cells send out special tips (growth cones) that extend through the extracellular compartment until they find their target cell
 connection between neurons must be active or the synapse will degrade
 babies are born with the same nerve cells as adults but they develop by making neural connections

5

glial cells

 support staff of the nervous system
 10-50x the number of cells as neurons
 Provide physical support
 Provide some communication and important biochemical support to neurons
 PNS: Schwann cells and satellite cells
CNS: astocytes, microglia, oligodendrocytes, ependymal cells

6

schwann cells

PNS glial cells
o Form myelin sheaths
o Leaves nodes of Ranvier (tiny gaps) between the myelin-insulated areas when wrapping around an axon
 Allows for a tiny section of axon membrane to be in direct contact with the extracellular fluid which plays a role in the transmission of electrical signals along the axon
o Secrete neurotrophic factors

7

satellite cells

PNS glial cells
o Nonmyelinating Schwann cell
o Support cell bodies in ganglion (clusters of nerve cell bodies outside the CNS)
o Provides structure and physical support

8

astocytes

o Highly branched glial cells that form a functional network by communicating with one another through gap junctions
o Several roles that the terminals could have
 Take up and release chemicals
 Provide neurons with substrates for ATP production to help maintain homeostasis in CNS
 Surround blood vessels and become part of the blood-brain barrier

9

microglia

CNS glial cell
modified immune cells that reside permanently in the CNS
o Scavenge whatever they think shouldn't be there
o Can release reactive oxygen species that can damage the CNS
 Plays a role in neural diseases

10

Oligodendrocytes

CNS glial cell
o Key difference between Schwann cells
 Schwann can only wrap around one axon
 Oligodendrocytes can wrap around several axon

11

ependymal cells

CNS glial cell
o Specialized cells that create a selectively permeable epithelial layer that separates the fluid compartments of the CNS
o Source of neural stem cells
o Communicate through chemical signals

12

CNS vs PNS glial cells

card image
13

myelin

a substance composed of multiple concentric layers of phospholipid membrane
 Acts as insulation around axons which speeds up their signal transduction
• Gap junctions connect the myelin membrane layers and allow the flow of nutrients and information from layer to layer

14

Ion movement

 Depolarization
• Move down concentration gradient
• Membrane potential increases (from lightly negative initial potential from Na+ going to ICF from ECF)
 Hyper polarization
• Remove K+ from ICF or add Cl- to ICF
• need to move very few ions to see a change in membrane potential
 Gated ion channels
• Named after the ion they are trying to move
mechanical, chemical or voltage
threshold voltage and speed for channel to open varies with channel type

15

graded potentials

variable-strength signals that travel over short distances and lose strength as they travel through the cell
 More stimulus = more signals being opened up= stronger signal
o If strong enough, reaches trigger zone
 If signal reaches threshold, Na+ channels open and AP starts
 If not strong enough nothing will happen

16

excitatory graded potential

 Excitability- the ability of a neuron to respond to a stimulus and fire an action potential
 Depolarizes membrane (local current flow)
 Brings closer to action potential threshold
 Positive ions (Na+)

17

inhibitory graded potential

 Hyperpolarizes membrane
 pushes away from action potential
 negative ions

18

subthreshold

a stimulus that is below threshold by the time it reaches the trigger zone
no AP

19

why do graded potentials lose strength?

 The membrane of neuron cell body has open leak channels that allow positive charge to leak out into the extracellular fluid
 Cytoplasm provides resistance to the flow of electricity

20

suprathreshold

a signal that is strong enough to cause and action potential by the time it reaches the trigger zone

21

action potentials

o Brief, large depolarization
o Long distances
o Signal strength is constant
o Starts at trigger zone, reaches end of axon
o Occur as a maximal depolarization (if the stimulus reaches threshold) or do not occur at all (if the stimulus is below threshold)
o All about moving ions
rising, peak, and falling phases
o A neuron could fire >1000 times without affection ion gradients

22

rising phase of action potential

• Overshoots following the concentration gradient because its following the electrical gradient as well
• Permeability to Na+ increases
• Na+ voltage-gated channels open

23

peak phase of action potential

• Na+ follows gradients to equilibrium point
• Na+ channels close
• K+ channels open

24

falling phase of action potential

• Permeability to K+ increases
• K+ voltage-gated channels open
• Follows electrical and concentration gradient out of axon
• Undershoots (hyperpolarization) following concentration gradient
• K+ channels close
• Na resets during refractory period
o 1/100,000 K+ leave cell during falling phase of action potential

25

refractory period

 Once an AP has started, cannot fire another for 1-2 msec.
 Absolute or relative refractory periods

26

absolute refractory period

• Na+ channels are not reset
• AP cannot happen
• AP moving from trigger zone to axon terminal cannot overlap and cannot travel backwards

27

relative refractory period

• Some Na+ channels have reset, K+ channels are still open
• Stronger than normal graded potential could trigger AP

28

things that make a signal faster

 Diameter of the axon affects speed of AP
• Larger axon diameter = less resistance = faster signal propagation
o Myelination
 Minimize ion leakage by minimizing contact with ECF
• Decreases membrane capacitance

29

abnormal electrical activity

blocked Na+ channels (anesthetics, neurotoxins)
ion concentrations in the ECF, specifically K+
hyperkalemia (too much K+ in ECF, depolarizes cells, lowers AP threshold)
hypokalemia (too little K+ in ECF, hyperpolarizes cells, raises AP threshold)

30

electrical synapses

o Pass signal through gap junctions directly from the cytoplasm of one cell to another
 Through pre and post synaptic cells
o CNS, glial cells, muscle, pancreatic beta cells
o Rapid signaling
o Relatively uncommon compared to chemical signals

31

chemical synapses

o Majority of synapses
neurocrine signals
 May act as neurotransmitters, Neuromodulators, or neurohormones

32

neuromodulators

• Usually act as paracrine signals (Can act as autocrine signals, but not common)
o Target cells located close the neuron that secreted them
• Act at both synaptic & non-synaptic sites (glial cells, etc. , not blood)
• Slower, longer lasting response than neurotransmitters

33

Ligand-gated ion channels

neurocrine receptor
• Ionotropic receptors
o Receptor-channels mediate rapid responses by altering ion flow across the membrane
• Neurotransmitter binds to channel, opens channel, allows ion to move into postsynaptic cell
• Rapid responses
• Quick to degrade

34

G protein-coupled neurocrine receptors

• Metabotropic receptors
o Regulate the opening and closing of ion channels
• Use second messenger system
• Slower responses than ligand-gated ion channels, longer lasting

35

neurotransmitters

 Act at a synapse- does not move through blood
 Quick, short acting response
 Seven classes based on structure
 PNS: Only 3 major neurocrines
 CNS: Release a variety of neurocrines
 Use a variety of receptors with specific names

36

neurotransmitter transport

can be peptide proteins or smaller neurotransmitters
o The action potential depolarizes the axon terminal
o The depolarization opens voltage-gated Ca2+ channels, and Ca2+ enter the cell
o Calcium entry triggers exocytosis of synaptic vesicle contents
o Neurotransmitter diffuses across the synaptic cleft and binds with receptors on the postsynaptic cell
o Neurotransmitter binding initiates a response in the postsynaptic cells
o endocytosis on the membrane then cell breaks away

37

nerve cell communication

divergent or convergent
integration of signals
spatial summation, temporal summation, postsynaptic inhibition, synaptic integration, presynaptic inhibition, presynaptic facilitation

38

divergent nerve cell signaling

a single presynaptic neuron branches, and its collaterals synapse on multiple target neurons

39

convergent nerve cell signaling

a group of presynaptic neurons provide input to a smaller number of postsynaptic neurons

40

spatial summation

type of nerve signal integration
o multiple excitatory neurons fire, their graded potentials separately are all below threshold
o Graded potentials arrive at a trigger zone together and sum to create and a suprathreshold signal
o An action potential is generated

41

temporal summation

type of nerve signal integration
o 2 subthreshold graded potentials from the same presynaptic neuron can be summed if they arrive at the trigger zone close enough together in time

42

postsynaptic inhibition

type of nerve signal integration
o The inhibitory postsynaptic potential (IPSP) counteracts the excitatory postsynaptic potential (EPSP)
o The summed potentials are below threshold, so no action potential is generated

43

synaptic integration

type of nerve signal integration
o When multiple signals reach a neuron, postsynaptic integration creates a signal based on the relative strengths and durations and compares the integrated signals to the threshold

44

presynaptic inhibition

type of nerve signal integration
o Activity in an inhibitory neuron decreases neurotransmitter release
o Allows selective modulation of collaterals and their targets
 One can be inhibited while others are unaffected

45

presynaptic facilitation

type of nerve signal integration
o Input from an excitatory neuron increases neurotransmitter release by the presynaptic cell

46

CNS organization

 Gray matter
• Unmyelinated nerve cell bodies, dendrites, & axon terminals
• Organized in layers or clusters (nuclei)
 White matter
• Myelinated axons and few cell bodies
• Tracts – bundles of axons that connect different regions of the CNS
 Brain and spinal cord are soft, contains little extracellular matrix
 Bone
• Brain – Skull, Spinal cord – Vertebral column

47

meninges

• 3 layers of membrane
• Connective tissue
• Lie between bones and tissues
• Stabilize neural tissue and protect from bruising by bones
• contains Dura mater, arachnoid, and pia mater

48

layers of meninges membrane

• Dura mater
o Thickest
o Drains blood from brain through cavities (sinuses)
• Arachnoid
o Middle membrane
cerebrospinal fluid is found between pia mater and arachnoid membrane
• Pia mater
o Thin membrane
o Arteries that supply blood found here, interstitial fluid found here

49

Cerebrospinal fluid (CSF)

secreted into the ventricles and flows throughout the subarachnoid space (between pia mater and arachnoid membrane), where it cushions the CNS

protection for CNS- buoyancy and padding

chemical- closely regulate the extracellular environment and exchange materials with the interstitial fluid of the CNS

50

blood-brain barrier

• Separates interstitial fluid and blood
• Barrier is necessary to isolate the body’s main control center from potentially harmful substances in the blood and from blood borne pathogens
• Capillaries with highly selective membranes

51

spinal cord

• Highway for information between brain & rest of body (skin, joints, and muscles)
• Contains neural networks for locomotion
• Self-regulated pathways for spinal reflexes
• Can also send signals to brain
• Divided into 4 regions: cervical, thoracic, lumbar, and sacral
 White matter- consists of tracts of axons carrying information to and from the brain
 Gray matter- sensory and motor nuclei

52

brain stem

 Similar in structure to the spinal cord
 Oldest, most primitive part
 Can be divided into white and gray matter (similar to spinal cord)
 Reticular formation, medulla, pons, midbrain, cerebellum, diencephalon, hypothalamus, cerebrum

53

Reticular formation

diffuse collection of neurons that extend throughout the brain stem
• Sleep/arousal, muscle tone, breathing, pain

54

medulla

• AKA medulla oblongata
• Transition between brain & spinal cord
• White matter- ascending somatosensory tracts bring sensory information to the brain and descending corticospinal tracts convey info from the cerebrum to the spinal cord
o 90% of corticospinal tracts crossover the midline to the opposite side of the body in pyramids section
o Create left and right brain that control the opposite side of the body
• Gray matter- Involuntary responses
o Blood pressure, Breathing, Swallowing, Vomiting

55

pons

• Relay station between cerebrum & cerebellum
• Works with medulla to help regulate breathing

56

midbrain

• Relay station for auditory and visual reflexes
• Controls eye movement

57

cerebellum

• Second largest part of brain
• Contains more nerve cells than rest of brain combined
• Process sensory info
• Coordinate movement

58

diencephalon

• Between brain stem and cerebellum
• Contains 2 main sections (thalamus and hypothalamus) and 2 endocrine structures (pituitary and pineal glands)

59

hypothalamus

• Activates sympathetic nervous system (catecholomine (flight or fight) release and maintaining blood glucose concentrations)
• Maintains body temperature
• Controls body osmolarity
• Controls reproductive functions
• Controls food intake
• Influences behavior and emotion with limbic system
• Influences cardiovascular control center in medulla
• Secretes trophic hormones that control the release of hormones in the pituitary gland

60

cerebrum

• Very furrowed surface (especially compared to mice/rats that have a very smooth surface)
• Two hemispheres connected by corpus callosum (structure formed by axons passing from one side of the brain to the other)
o Ensures the 2 hemispheres communicate and cooperate
• Cerebral gray matter
o Cerebral cortex- outer layer of the cerebrum (contains layered neurons where higher brain function arises)
 Perception
 Movement
o Basal ganglia
 Movement
o Limbic system
• Cerebral white matter- axons themselves
o white and grey matter alternate in layers

61

thalamus

• Lots of sensory information comes in and the thalamus will relay the information
o Thalamus can modify and integrate the information
o Relay station
 Eyes, Ears, Spinal cord, Motor (from cerebellum)
 Projects fibers to the cerebrum where the information is processed
 All sensory information from the lower parts of the CNS pass through the thalamus
o Integrating center

62

limbic system

surrounds brain stem
 Link between higher cognitive functions (like reasoning) and more primitive emotional responses (fear)
 Emotion (amygdale and cingulated gyrus)
 Memory(amygdale, cingulated gyrus, hippocampus)
 Learning (hippocampus)

63

cerebral lateralization

• asymmetrical distribution of functional specialization
• each lobe has special functions not shared by the matching lobe on the opposite side
• the specialization can change, you can build new connections
• Right handed = left brain dominant

64

cerebral cortex

integrating center for sensory information and a decision-making region for many types of motor output

sensor

65

motor output

 directs skeletal muscle movement
 Part of efferent division of nervous system
 3 types: skeletal movement, neurocrine signals, and visceral responses
• neurocrine and visceral responses are coordinated primarily by the primary motor cortex and the medulla

66

3 types of motor output

• skeletal movement- controlled by the somatic motor division
• neurocrine signals- neurohormones secreted into the blood by neurons located primarily in the hypothalamus and adrenal medulla
• visceral responses- the actions of smooth and cardiac muscle or endocrine and exocrine glands (muscles, organs)

67

Diffuse modulatory systems

part of behavioral state systems

neurons that originate in the reticular formation in the brain stem and project their axons to large areas of the brain

o Named based on neurotransmitter they release
o Influence motivation, memory, sleep, etc.

68

sleep

• Easily reversible state of inactivity characterized by lack of interaction with external environment
• sleep releases molecules that assist your immune system
• non-REM sleep (deep sleep) and REM sleep

69

circadian rhythm

o alternating daily pattern of rest & activity
o Regulated by suprachiasmatic nucleus of the hypothalamus
o Feedback loop
 Genes turn on, direct protein synthesis
 Protein accumulates, turns off genes
 Protein degrades, turning back on genes
o Synchronized with the sensory info about light cycles received through the eyes

70

sensory receptors

 Variable and specialized
• Receptors can be stimulated by other stimuli sometimes
 Includes non-neural cells
 Accessory structures
 Convert stimulus into neural signal

71

receptive fields

• Physical area covered by sensory neuron
• Primary sensory neuron- one receptive field associated with one sensory neuron
• Secondary sensory neuron- synapses in the CNS neuron

72

CNS sensory processing

• Sensory neuron sends info to thalamus
• Thalamus processes & relays to appropriate CNS structure
 Synapse in the thalamus and then signal is passed on to another location

73

habituation

o Inhibitory modulation
o Suprathreshold stimulus pushed below perceptual threshold

74

How does your body tell stimuli apart?

 Sensory modality (nature of sensory stimuli)
 Sensory location
 Stimulus intensity
 Stimulus duration

75

sensory modality

helps your body tell signals apart
o The modality is indicated by which sensory neurons are activated and by where the pathways of the activated neurons terminate in the brain
 Connected to specific regions of the sensory cortex

76

sensory location

helps your body tell signals apart
connected to specific regions of the sensory sortex
lateral inhibition

77

stimulus intensity

helps your body tell signals apart
• The number of receptors activated
• Frequency of action potentials coming from those receptors (frequency coding)

78

stimulus duration

helps your body tell signals apart
• Longer stimulation à more APs in sensory neuron

adaption, tonic receptors, phasic receptors

79

lateral inhibition

o Primary neuron response is proportional to stimulus strength
o Pathway closest to the stimulus inhibits neighbors
o Inhibition of lateral neurons enhances perception of stimulus
o Secondary neuron that is most activated had post synaptic inhibition which causes only the strongest cells from the sensory neuron

80

tonic receptors

slow adapting receptors that fire rapidly when first activated, then slow and maintain their firing as long as the stimulus is present

81

phasic receptors

rapidly adapting receptors that fire when they first receive a stimulus but cease firing if the strength of the stimulus remains constant

82

somatosensory pathways

• Pain, temperature, and coarse touch cross the midline of the spinal cord
o Synapse onto their secondary neurons shortly after entering the spinal cord
• Fine touch, vibration, and proprioception pathways cross the midline in the medulla
• Sensory pathways synapse in the thalamus
• Sensations are perceived in the primary somatic sensory cortex

83

somatic senses

touch, proprioception (awareness of surroundings), temperature, nociception

84

touch somatic sense

 Responds to:
• Stretch: Ruffini corpuscle- slow adaption
• Pressure: Merkel receptors- slow adaption
• Stroking: Meissner’s corpuscle- rapid adaption
• Vibration: Pacinian corpuscle- rapidly adapting phasic receptors
o Can respond to a change in touch then ignore it

85

temperature somatic sense

 Free nerve endings in subcutaneous layer of skin
 More cold than warm receptors
• Cold receptors – sense below body temp
• Warm receptors – sense between body temp & 45°C
• > 45°C – pains receptors activated
 Slowly adapt between 20-40°C, otherwise do not adapt

86

nociception somatic sense

 Respond to damaging stimuli via pain and itch
• Chemical, mechanical, & thermal
 Found throughout body, not just skin
 2 pathways: Reflexive protective (spinal cord), Conscious sensation in the cerebral cortex (CNS)

87

pain

• Pain is not a direct stimulus, but a perception
• Nociceptors send info to CNS via A-delta & C fibers
o Fast pain – sharp, localized – rapidly signals CNS via myelinated A-delta fibers
o Slow pain – dull, diffuse – signals CNS via unmyelinated C fibers
• Signals limbic system & hypothalamus too
• Treated with aspirin, opioids or other drugs, electrical stimulation, or severing sensory nerves

88

itching

o Signal carried to CNS via subtype of C fiber
o Antagonistic interaction with pain
 When something itches, we scratch it creating a sensation of pain to stop the itch
• Works in the other direction too

89

Olfactory bulb

extension of forebrain that sends info to olfactory cortex
 Receives input from the primary olfactory neurons

90

olfactory transduction

o Primary sensory neurons (olfactory sensory neurons) synapse with secondary in olfactory bulb which moves towards the olfactory cortex via the olfactory tract
 can be routed to the hippocampus and amygdale (limbic system involved in emotion and memory)
 bypasses the thalamus

91

olfactory sensory receptors

 Odorant receptors- protein receptor that is sensitive to a variety of substances
• G-protein coupled receptors
• Largest gene family in vertebrates

92

olfaction signal processing

 Each olfactory sensory neuron has one type of odorant receptor
 Convergence of many primary sensory neurons to a few secondary neurons in olfactory bulb which modifies the info and sends it to the olfactory cortex
 Olfactory cortex uses hundreds of signals in different combinations to create perception of smells

93

taste sensations

 Sweet – nutritious organic molecules
 Umami – glutamate (MSG)
 Bitter – toxic organic molecules
 Sour – excess H+
 Salty – excess Na+

94

taste anatomy

 Taste buds (taste receptors) located in surface of tongue
 Not neural cells, specialized taste cells
 Taste bud= 50-150 taste cells + support and regenerate cells
 Taste pore is the only area of the cell that is exposed to the external environment
 Dissolved particles (food dissolved by saliva) interact with apical membrane protein on a taste cell
 Each taste cell is sensitive to one taste

95

types of taste cells

 4 cell types:
• 1- support cells- may sense salt when Na+ enters through Na+ channels
• 2- receptor cells- respond to sweet, bitter, and umami sensations
o Releases ATP through gap junctions and ATP acts on both sensory neurons and neighboring presynaptic cells
• 3- presynaptic cells- perceive sour, synapse with sensory neurons
• 4 basal cells- give rise to new taste cells

96

tast transduction

• ligands activate the taste cell
• various intracellular pathways are activated
• Ca2+ signal in the cytoplasm triggers exocytosis or ATP formation
• Neurotransmitter or ATP is released
• Primary sensory neuron fires and action potentials are sent to the brain

97

hearing

o Perception of energy delivered by sound waves
o Sound- the brain’s interpretation of the frequency and duration of sound waves
 Interpretation of frequency (pitch), intensity and amplitude (loudness), and duration

98

hearing anatomy

card image

Tympanic membrane= eardrum

99

special senses

smell, taste, hearing, equilibrium, vision

100

sound transduction

o Energy from sound waved in the air becomes mechanical vibrations, then fluid waves in the cochlea
o The fluid waves open ion channels in hair cells (sensory receptors for hearing)
o Ion flow into hair cells creates electrical signals that release neurotransmitter (chemical signal) which triggers action potentials in the primary auditory nerves

101

hearing loss

• Conductive
o No sound transmission through external or middle ear
o Perfect suction cup around ear can pop the ear drum
• Central
o Damage to neural pathways or cortex- caused by strokes, brain trauma
• Sensorineural
o Damage to inner ear structures
o 90% of hearing loss

102

equilibrium

 Balance- Position of body in space
 Stimuli- Changes in gravity and acceleration
 3 Semicircular canals

103

3 sensory canals of equilibrium

• Rotational acceleration
• Horizontal- shaking head side to side (“no”)
• Superior- nodding back and forth (“yes”)
• Posterior- head towards right or left shoulder

104

equilibrium sensory processing

• Vestibular hair cells release neurotransmitters to the primary sensory neurons of the vestibular nerve which lead to the cerebellum for equilibrium processing

105

vision

o Translation of light reflected from objects into a mental image
 Light enters eye, lens focuses light on retina
 Photoreceptors transform light into electrical signal
 CNS processes electrical signals into visual images

106

vision anatomy

card image
107

light modulation

size of pupil (radial muscles control the contracting and expanding with changes)

change shape of lens (accommodation, ciliary muscles flatten and curl lens)

108

phototransduction

• Light from a fixation point passes through the lens which focuses the light on the retina and fovea
• The projected image is upside down on the retina
o Visual processing in the brain reverses the image
• Retina photoreceptors are organized in layers
• Light strikes the photoreceptors in the fovea directly because overlying neurons are pushed aside
• There are 3 types of cone pigment (blue, green, and red), each with a characteristic light absorption spectrum

109

visual signal processing

• Two types of bipolar cells
o Bipolar cells- begins signal processing when glutamate is released from photoreceptors
 Light-on (excited by glutamate inhibition)
 Light-off (excited by glutamate release)
• Ganglion cells- Receive signals from area of photoreceptors on retina called visual field
• Visual fields are smaller towards fovea, larger towards outer portions of retina

110

3 systems that influence output by the motor systems of the body

 Sensory system- monitors the internal and external environments and initiates reflex responses
 Cognitive system- resides in the cerebral cortex and is able to initiate voluntary responses
 Behavioral state system- resides in the brain and governs sleep-wake cycles and other intrinsic behaviors

111

transduction

conversion of stimulus energy into information that can be processed by the nervous system
o Often the opening or closing of ion channels

112

somatic motor division

 Controls skeletal muscle
 “Voluntary” division of nervous system

113

The neuromuscular junction (NMJ)

consists of axon terminals, motor end plates on the muscle membrane, and Schwann cell sheaths
• 3 components
o The motor neuron’s presynaptic axon terminal filled with synaptic vesicles and mitochondria
o Synaptic cleft
o Postsynaptic membrane of the skeletal muscle fiber

114

autonomic division

 Controls smooth muscle, cardiac muscle, many glands, some adipose tissue
 “Involuntary” division of nervous system
sympathetic or parasymptathetic

115

sympathetic division

autonomic pathways
• Dominant in stressful situations
• Fight or flight response
• Provides stimulation or control during most of the time

116

parasympathetic

autonomic pathways
• Dominant in calm situations
• Rest & digest response
• Active almost all the time

117

autonomic division

• homeostasis-
o Works closely with the endocrine and behavioral state system to maintain homeostasis in the body
 Homeostatic control centers: hypothalamus (contains osmoreceptors and thermoreceptors), medulla, pons
• Reflex responses- some autonomic reflexes are capable of taking place without input from the brain (spinal reflexes)
• Behavioral responses- emotional influences on autonomic functions

118

antagonistic autonomic control

• one autonomic branch is excitatory and the other branch is inhibitory
• Often sympathetic & parasympathetic control act in opposite directions on same tissue
• Regulate by altering amount of control given to each branch
• Receptor type can determine response

119

neuroeffector junctions

Synapse between a postganglionic autonomic neuron & target cell
varicosities
o No high concentration of receptors in target cells during autonomic response (like in other responses)

120

Varicosity

swollen area at distal end of postganglionic axons
 Filled with neurotransmitters and mitochondria
 Will surround the target tissue

121

adrenal medulla

o Neuroendocrine tissue associated with sympathetic nervous system
o Secretes epinephrine- system wide response
 Secretes norepinephrine, catecholamines, and epinephrine during development
o Neural and endocrine tissue (similar to pituitary gland)

122

Sympathetic vs parasympathetic branches

card image
123

somatic motor and autonomic divisions

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124

adrenergic receptors

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125

Sympathetic and Parasympathetic pathways

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