Neurological System
ANATOMY AND PHYSIOLOGY OF THE BRAIN AND SPINAL CORD
Cerebrum
- The 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 cerebral cortex is the outer gray layer; it is divided into five lobes.
- It is responsible for the conscious activities of the cerebrum.
Basal ganglia:
Cell bodies in white matter that help the cerebral cortex produce smooth voluntarymovements
Diencephalon
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 secreted by the pituitary gland and the hypothalamus
Brainstem
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 smooth 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, and adipose tissue
Horns
- Inner column of gray matter; contains two anterior and two posterior horns
- Posterior horns connect with afferent (sensory) nerve fibers.
- Anterior horns contain efferent (motor) nerve fibers.
Nerve tracts
- White matter contains the nerve tract.
- Ascending tracts (sensory pathway)
- Descending tract (motor pathway)
Meninges
- Dura mater is the tough and fibrous membrane.
- Arachnoid membrane is the delicate membrane and contains cerebrospinal fluid.
- Pia mater is the vascular membrane.
- Subarachnoid space is 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 layer of the meninges, where it is reabsorbed
- Acts as a protective cushion; aids in the exchange of nutrients and wastes
- Normal pressure is 50 to 175 mm H2O.
- Normal volume is 125 to 150 mL.
Ventricles
- Four ventricles
- The ventricles communicate between the subarachnoid spaces and produce and circulate cerebrospinal fluid.
Cerebral Cortex
- Frontal Lobe
- Broca’s area for 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 sensory and speech
- Occipital Lobe
- Visual area
- Limbic System
- Emotional and visceral patterns for survival
- Learning and memory
Blood supply
- Right and left internal carotid arteries
- Right and left vertebral arteries
- These arteries supply the brain via an anastomosis at the base of the brain called the circle of Willis.
Neurotransmitters
- Acetylcholine
- Norepinephrine
- Dopamine
- Serotonin
- Amino acids
- Polypeptides
Neurons
- The neuron consists of the cell body, axons, and dendrites.
- The cell body contains the nucleus.
- Neurons carrying impulses to the central nervous system (CNS) are called sensory neurons.
- Neurons carrying impulses away from the CNS are called motor neurons.
- Synapse is the chemical transmission of impulses from one neuron to another.
Axons and dendrites
- The axon conducts impulses from the cell body.
- The dendrites receive stimuli from the body and transmit them to the axon.
- The neurons are protected and insulated by Schwann cells.
- The Schwann cell sheath is called the neurolemma.
- Neurons do not reproduce after the neonatal period.
- If an axon or dendrite is damaged, it will die and be replaced slowly only if the neurolemma is intact and the cell body has not died.
Spinal nerves
- There are 31 pairs of spinal nerves.
- Mixed nerve fibers are 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
- Sympathetic (adrenergic) fibers dilate pupils, increase heart rate and rhythm, contract blood vessels, and relax smooth muscles of the bronchi.
- Parasympathetic (cholinergic) fibers produce the opposite effect.
