Download lec13

Chapter 13
Anatomy & Physiology
Fifth Edition
Seeley/Stephens/Tate
(c) The McGraw-Hill Companies, Inc.
• Major divisions and their functions of the Brain
– Study Table 13.2 carefully. They are reinstated below.
• Brainstem
• The information processing center connection between the
cerebrum and the spinal cord. Location of cranial nerve nuclei.
• Medulla Oblongata
• The most inferior portion of the brainstem.
• Ascending and descending nerve tracts
• Autonomic control centers for heart beat, breathing, blood
pressure.
• Reflex control center for coughing, sneezing and swallowing.
• Pons
–
–
–
–
It is a bridge to cerebellum.
Ascending and descending nerve tracts.
Control breathing and sleep activity.
Controlling chewing and sleep activity.
• Midbrain
–
–
–
–
Top of the brainstem.
Ascending and descending nerve tracts.
Visual and auditory information.
Generates involuntary motor responses, such as muscle tone
and posture.
– Maintenance of consciousness.
• Reticular formation
– Scattered throughout the brainstem.
– Controls cyclic activities, such as the sleep/wake cycle.
• Diencephalon
• Connected to cerebrum
– Thalamus
• A relay and processing centers for sensory information.,mood and
movement.
– Subthalamus
• Nerve tracts and nuclei.
– Epithalamus
• Nuclei for olfactory stimulation and contains pineal body.
– Hypothalamus
• Centers for emotion, autonomic function, such as regulation of
body temperature and appetite, and hormone production.
• Generates emotional and sexual responses.
• Endocrine: the pituitary gland connects neurons to hormones.
• Regulation of sleep and wake cycle.
• Cerebrum
– A pair of not necessarily symmetric cerebral
hemispheres.
– The thinking part. Center of intellect. Memory,
language, sensory perception, control of skeletal
muscles.
– Can override most other systems
– Cerebral cortex, i.e grey matter (soma of neurons)
• Basal nuclei
– Muscle activity and posture.
– Largely inhibit unintentional movement.
• Limbic System
– Autonomic responses to smell, emotion, mood and
other such functions.
• Cerebellum
– Responsible for coordinating and modifying
somatomotor impulses to produce smooth
coordinated skeletal muscle movements.
– Adjusts voluntary and involuntary activities on the
basis of sensory information and stores memories of
previous movements.
– See figure 13.17 for cerebellar comparator function.
• More about cerebrum
– The largest portion of the brain. 1400g for males and 1200g for
females.
– The grey matter: the outer surface of the cerebrum, the cortex.
The grey matters deep inside the cerebrum are nuclei.
– The white matter; the cerebral medulla consisting of nerve
tracts. There are three tracts; a) association fibers connecting
within the same hemisphere, b) commissural fibers connecting
the two hemispheres, c) projection fibers between the cerebrum
and other CNS. (fig 13.9)
– Study fig. 13.10 for the lateral side of the left cerebral cortex,
where functional areas are found.
– Also note the relative positions of somatic sensory and motor
cortex of the left side of the brain (fig.13.11).
• Memory
– There are three types: sensory, short-term, and long term.
– Sensory memory – is less than a second. Transient scanning
appears as quick change in membrane potentials.
– Short-term memory – is important enough sensory memory
and may be retained for a few seconds to a few minutes. Seven
bits or more.
– Long-term memory – may include a physical change in
neuron shape- long term potentiation. The shape of a neuron is
changed by calpain and neurons may form a memory engram.
There are two type of long term memory: declarative memory
for facts in the hippocampus and for emotion in amygdaliod
nucleus, and procedural memory (reflex memory) for
development of skills in the cerebellum and premotor area of
the cerebrum. (recall Pavlov’s experiment with the dogs)
PNS AND INTERGRATED NEURONAL FUNCTIONS
• Structure of spinal cord will be covered on lab.
• Another important function of the neuronal system is
the communication between the CNS and PNS.
• They create pathways and circuits.
• A sensory receptor ascends sensory pathway (afferent
division) through the medulla and the thalamus before
reaching the cerebral cortex for final processing.
• Then descends through motor pathway (efferent
division) to effector tissue or organs.
• We will study the PNS, then their integrated functions
with the CNS.
• The peripheral nervous system
• The PNS includes all the neurons other than those of the
CNS, and is inclusive of the cell bodies and the axons of
sensory neurons.
• The cranial nerves
• The peripheral nerves may be connected to the CNS
through the spinal cord or directly.
• The cranial nerves are those directly connect to the
brain. There are 12 pairs and are identified with N and
Roman numeral, i.e. NI – N XII.
• A cross sectional figure of the spinal cord (13.19)
• All together there are 31 pairs of spinal nerve groups
identified according to the region of the spinal cord
where they are found, such as:
– 8 pairs of cervical nerves: up to C8
– 12 pairs of thoracic nerves: up to T12
– 5 pairs of lumbar nerves: up to L5
– 5 pairs of sacral nerves: up to S5
– A pair of coccygeal nerves: Co1
The End.