Anatomy and Physiology of the Brain and Spinal Cord

Cerebrum

• consists of the right and left hemispheres.

• Each hemisphere receives sensory information from the opposite side of the body and controls the skeletal muscles of the opposite side.

• The cerebrum governs sensory and motor activity and thought and learning.

Cerebral cortex

• the outer gray layer; it is divided into 5 lobes.

• It is responsible for the conscious activities of the cerebrum.

Frontal Lobe

• Broca’s area for production of speech

• Morals, emotions, reasoning and judgment, concentration, and abstraction

Parietal Lobe

• Interpretation of taste, pain, touch, temperature, and pressure

• Spatial perception

Temporal Lobe

• Auditory center

• Wernicke’s area for comprehension of speech

Occipital Lobe

• Visual area

Limbic System

• Emotional and visceral patterns for survival

• Learning and memory

Basal ganglia

Cell bodies in white matter that help the cerebral cortex to produce smooth voluntary movements

Diencephalon

• Thalamus and Hypothalamus

Thalamus

• Relays sensory impulses to the cortex

• Provides a pain gate

• Part of the reticular activating system

Hypothalamus

• Regulates autonomic responses of the sympathetic and parasympathetic nervous systems

• Regulates the stress response, sleep, appetite, body temperature, fluid balance, and emotions

• Responsible for the production of hormones

Brainstem

• Midbrain

• Pons

• Medulla oblongata

Midbrain

• Responsible for motor coordination

• Contains the visual reflex and auditory relay centers

Pons

Contains the respiratory centers and regulates breathing

Medulla oblongata

• Contains all afferent and efferent tracts and cardiac, respiratory, vomiting, and vasomotor centers

• Controls heart rate, respiration, blood vessel diameter, sneezing, swallowing, vomiting, and coughing

Cerebellum

Coordinates muscle movement, posture, equilibrium, and muscle tone

Spinal cord

• Provides neuron and synapse networks to produce involuntary responses to sensory stimulation

• Controls body movement and regulates visceral function

• Carries sensory information to and motor information from the brain

• Extends from the first cervical to the second lumbar vertebra

• Protected by the meninges, cerebrospinal fluid (CSF), and adipose tissue

Spinal Cord: Horns

• a. Inner column of gray matter; contains 2 anterior and 2 posterior horns

• Posterior horns connect with afferent (sensory) nerve fibers.

• Anterior horns contain efferent (motor) nerve fibers.

Nerve tracts

• White matter contains the nerve tracts.

• Ascending tracts (sensory pathway)

• Descending tracts (motor pathway)

Sensory

Afferent nerve fibers

Motor

Efferent nerve fibers

Motor pathway

Nerve tracts: Descending tracts

Sensory pathway

Nerve tracts: Ascending tracts

Meninges

• dura mater

• arachnoid membrane

• pia mater

• subarachnoid space

Dura mater

Meninges: a tough and fibrous membrane.

Arachnoid membrane

a delicate membrane and contains CSF.

PIa mater

Meninges: vascular membrane

Subarachnoid space

formed by the arachnoid membrane and the pia mater.

Cerebrospinal fluid (CSF)

• Secreted in the ventricles; circulates in the subarachnoid space and through the ventricles to the subarachnoid space of the meninges, where it is reabsorbed

  • Acts as a protective cushion; aids in the exchange of nutrients and wastes

50 to 175 mm H2O

Normal pressure of CSF

125 to 150 mL

Normal volume od CSF

Ventricles of the brain

• 4

• communicate between the subarachnoid spaces and produce and circulate CSF

Lateral ventricles

the largest ventricles located in the cerebrum, one in each cerebral hemisphere

Third ventricle

Located in the diencephalon, between the thalamus

Fourth ventricle

located in the hindbrain, at the back of the pons and upper medulla oblongata

sensory neurons

Neurons carrying impulses from the peripheral nervous system to the central nervous system (CNS)

motor neurons

Neurons carrying impulses away from the CNS

Synapse

the chemical transmission of impulses from 1 neuron to another.

axon

conducts impulses from the cell body

dendrites

receive stimuli from the body and transmit them to the axon.

neurolemma

The Schwann cell sheath is called

31

how many pairs of spinal nerves

Mixed nerve fibers

formed by the joining of the anterior motor and posterior sensory roots.

Posterior roots

contain afferent (sensory) nerve fibers

Anterior roots

contain efferent (motor) nerve fibers.

Autonomic nervous system

• SNS (adrenergic) and PSNS (cholinergic)