Chapter 12: NEURAL TISSUE, PPT
Cell body
integrate incoming signals that Contains an abundance of mitochondria, fixed and free ribosomes and RER (Nissl bodies), but lack centrioles
Dendrites
- Act as ‘receptors’
- Extend out from the cell body and branch into dendritic spines; account for 80-90% of the total surface area of a neuron
Axon (“nerve fiber”)
- Propagates electrical impulses known as action potentials
Axon (“nerve fiber”) associated
Initial segment, Axon collaterals, Telodendria, Synaptic knob
Initial segment of axon
joins the cell body at the axon hillock
Axon collaterals
branches of an axon; enable communication with more than one cell
Telodendria
terminal, finger-like projections of the axon
Synaptic knob
at the end of a telodendrion; contain vesicles full of neurotransmitters
Synaptic knob includes
- Presynaptic neuron
• Postsynaptic neuron
• Neuromuscular junction
• Neuroglandular junction
Sensory
Roughly 10 million sensory neurons transmit electrical impulses along afferent fibers from sensory receptors in the PNS into the CNS
sensory ganglia
Cell bodies in collections outside of the CNS
Interoceptors
monitor respiratory, digestive, cardiovascular, reproductive, and urinary systems; deep pressure, distension and pain
Exteroceptors
monitor stimuli from outside the body, i.e. pressure, temperature, touch, smell, vision, hearing, taste and equilibrium
Proprioceptors
monitor position and movement of skeletal muscles and joints
Motor neuron
Roughly 500,000 motor neurons transmit electrical impulses along efferent fibers from the CNS through the PNS to effectors (i.e. muscle, glands, adipose tissue)
nuclei (nucleus)
Cell bodies in collections inside of the CNS
Interneurons
Roughly 20 billion, most of which are found in the CNS
- Distribute sensory input and coordinate motor output
Sensory (afferent) division includes
Somatic and Visceral
Sensory - Somatic
signals from receptors in skin, muscle, and joints
Sensory -Visceral
signals from receptors in heart, lungs, digestive organs, bladder
Motor (efferent) division
Somatic and Visceral (autonomic)
Motor-Somatic
signals to skeletal muscles for voluntary contraction and involuntary somatic reflexes
Motor- Visceral (autonomic)
signals to glands, cardiac, and smooth muscle; primarily involuntary:
- Sympathetic: fight or flight division
- Parasympathtic: rest and digest division