Download Chapter 12-13 Summary

SUBJECT: ANATOMY & PHYSIOLOGY
BIOL 2404-I02
Chapter 12-13
NOTE: This was originally prepared for BIOL 2404, however many
parts overlap with 2401. I’ve added additional references. Use
this knowing it may not cover everything.
Nervous System: (These are very important chapters.)
1.
Organization of the Nervous System (Review Figure 12.1)
A. Structural: all nervous system structures are classified as part of the CNS (brain
and spinal cord) or the PNS (nerve and ganglion).
B. Functional: motor nerves of the PNS are classified on the basis of whether they
stimulate skeletal muscle (somatic division) or smooth\cardiac muscle and glands
(autonomic division).
2. Nervous tissue: Structure and Function
Supporting connective tissue cells
A.
I.
Neuroglia support protect neurons in the CNS. Specific glial cells are
phagocytes; other myelinate neuron processes in the CNS or line cavities.
II. Schwann cells myelinated neuron processes in the PNS.
III. Make a Table of neuroglia with function and location. (See Table 12.2)
B. Neurons (Review Figure 12.2 & 12.22)
i.
Anatomy: all neurons have a cell body which contains the nucleus and
processes (fibers of two types: (1) axons (one personnel) typically generate
and conduct impulses away from the cell body and release a
neurotransmitter, and (2) dendrites ( 1 to many per cell) typically carry
electrical currents toward the cell body. Most large fibers are myelinated;
myelin increases the rate of nerve impulse transmission.
ii. Classification
1.
On the basis of function (direction of impulse transmission) there are
sensory (afferent) and motor (afferent) neurons and interneurons
(association neurons). Dendritic endings of sensory neurons are bare
(pain receptors) or are associated with sensory receptors.
2.
On the basis of structure, the are unipolar, bipolar, and multipolar
neurons; the terminology reveals the number of processes extending
from the cell body. Motor and inter-neurons are multipolar; most sensory
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DR. DAVID L. COX
SUBJECT: ANATOMY & PHYSIOLOGY
BIOL 2404-I02
neurons are unipolar the exceptions are sensory neurons and certain
special sense organs ( ear, eye) which are bipolar. (Review Table 12.1)
iii. Physiology
i.
A nerve impulse is an electrochemical event (initiated by various stimuli)
that cause a change in neural plasma membrane permeability. This
change allows sodium ions to enter the cell, causing depolarization. Once
begun the action potential or nerve impulse continues over the entire
surface of the axon. Electrical condition of resting state are restored by the
diffusion of potassium ions out of the cell (repolarization) ion
concentrations of the resting state are restored by the sodium potassium
pump. (Review NAP handout and Figures 12.10 - 12.11)
ii. A neuron influences other neurons or effector cells by releasing
neurotransmitters, chemicals that diffuse across the synaptic cleft and
attach to membrane receptors on the postsynaptic cell. The result is
opening specific ion channels and activation or inhibition, depending on
the neurotransmitter released in the target cell. (Review Table 12.4).
Central Nervous System
3.
A.
The brain is located within the cranial cavity of the skull and consists of the
cerebral hemispheres, diencephalon, brainstem structures, and cerebellum.
i.
The two cerebral hemispheres are the largest part of the brain. Their
surface or cortex is gray matter, and their interior if white matter. The cortex is
convoluted and has gyri, sulci, and fissures. The cerebral hemispheres are
involved in logical reasoning, moral conduct, emotional responses, sensory
interpretation, and initiation of voluntary muscle activity. Several functional
areas of the cerebral lobes had been identified. (See page 242).
ii. The diencephalon is superior to the brain stem and is enclosed by the
cerebral hemispheres. the major structures include:
1. The thalamus, which encloses the third ventricle; is the relay station for
sensory impulses passing to the sensory cortex for interpretation.
2. The hypothalamus makes up the floor of the third ventricle and is the most
important regulatory center of the autonomic nervous system (regulates
water balance, metabolism, thirst, temperature, and the like).
3. The epithalamus includes the pineal gland (an endocrine gland gland)
and the choroid plexus of the third ventricle.
iii. The brainstem is a short region inferior to the hypothalamus that merges with
the spinal cord.
1. The midbrain is the most superior and is primarily fiber tracts.
2. The pons is inferior to the midbrain and has fiber tracts and nuclei involved
in respiration.
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DR. DAVID L. COX
SUBJECT: ANATOMY & PHYSIOLOGY
BIOL 2404-I02
3. The medulla oblongata is the most inferior part of the brain stem. In
addition to fiber tracts, it contains autonomic nuclei involved in the
regulation of vital life activities (breathing, heart rate, blood pressure, etc.).
iv. The cerebellum is a large, cauliflower – like part of the brain posterior to the
fourth ventricle. The coordinates muscle activity and body balance.
(Review Figure 13.1 and Table 7.1)
B. Protection of the CNS
i.
Bones of the skull and vertebral column are most external protective
structures.
ii.
Meninges are three connective tissue membranes – dura mater (tough, outer
most), arachnoid mater (middle, weblike), and pia mater (innermost,
delicate). The meninges extend beyond the end of the spinal cord. (Review
Figure 7.17)
iii. Cerebral spinal fluid (CSF) provides a watery cushion around the brain and
cord. CSF is formed by the choroid plexus of the brain. It is found in the
subarachnoid space, ventricles, and central canal of the spinal cord. CSF is a
continually formed and drained.
iv. The blood brain barrier is composed of relatively impermeable capillaries.
C. Review brain regions and functions. I suggest making a Table.
D. Review the terms of Chapter 12-13...
E.
Brain dysfunctions and embryonic development – skip.
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DR. DAVID L. COX
SUBJECT: ANATOMY & PHYSIOLOGY
BIOL 2404-I02
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DR. DAVID L. COX