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.