MCAT: Foundation 3

Nervous System:

a network of specialized cells that transmit signals throughout the body to control and coordinate bodily functions

Central Nervous System:

consists of the brain and spinal cord; it processes information and coordinates activity

Peripheral Nervous System:

includes all nerves and ganglia outside the central nervous system, connects it to all the limbs and organs

Brain:

section of the central nervous system of a vertebrate that is enclosed in the cranium and composed of grey and white matter

Cerebrum:

largest part of the brain, responsible for higher brain function like thought, memory, and voluntary movement

Thalamus:

the section in the forebrain that sends sensory signals to the correct locations in the brain

Basal Ganglia:

smoothen movements and maintain postural stability 

Limbic system:

contain septal nuclei, amygdala, and hippocampus controls emotions and memory 

Septal nuclei:

feelings of pleasure and pleasure seeking behavior 

Amygdala:

controls fear and aggression 

Hippocampus:

consolidates memories and communicates with other parts of the limbic system through the fornix

Cerebral cortex:

divided into four lobes 

Frontal Lobe:

executive function, impulse control, long term planning, and motor function 

Parietal Lobe:

sensations of touch, pressure temp., and pain 

Occipital Lobe:

controls visual processing 

Temporal Lobe:

controls sound processing, speech perception, and memory/emotion

Hypothalamus:

the section of the forebrain that controls hunger, thirst, and body temperature, commands the pituitary gland

Pituitary Gland:

the section of the forebrain the controls glands in the body and releases hormones

Cerebral Hemispheres:  

the left and right halves of the cerebrum

Brain Stem:

connects the brain to the spinal cord and controls basic life 

Midbrain:

mesencephalon, top portion of the brain stem involved in vision, hearing, and motor control

Pons:

middle part of the brain stem, relays signals from the forebrain to the cerebellum

Medulla Oblongata:

medulla, lower part of the brain stem responsible for regulating breathing, heart rate, and digestion

Cerebellum:

located behind the brain stem; responsible for coordination and balance

Spinal Cord:

a long tube of nerve tissue running down the spine; transmits signals between the brain and the body

Forebrain:

prosencephalon, becomes the cerebrum

Midbrain:

mesencephalon, becomes the midbrain

Hindbrain:

rhombencephalon, becomes the pons, medulla, and cerebellum

Nerve:

a bundle of axons that carry signals throughout the body

Ganglion:

a cluster of neuron somas in the peripheral nervous system

Cranial Nerves:

12 pairs of nerves that emerge from the brain/skull

Spinal Nerves:

31 pairs of nerves that emerge from the spinal cord

Spinal Nerve Roots:

two roots that merge to form the spinal nerves, front and back

Dorsal Root:

back spinal nerve that carries afferent sensory signals

Ventral Root:

front spinal nerve that carries efferent motor

Mixed Nerve:

a nerve that contains both afferent and efferent axons

Afferent Neurons:

carries sensory signals into the CNS from the periphery

Efferent Neurons:

carry motor signals away from the CNS to the periphery 

Proximal:

closer to the center of the body or point of origin

Distal:

farther from the center of the body or the point of origin

Axon:

a long projection of a neuron that conducts electrical impulses

Soma:

the cell body of a neuron containing the nucleus

Basic Nervous Functions:

performed by the CNS and the PNS

Motor Functions:

refers to control of the skeletal muscle and enables bodily movement 

Skeletal Muscle:

muscles that control movement , tone, and posture that are attached to bone

Sensory Functions:

involves the detection of stimuli, internal and external by the nervous system

Vision, Sight, Hearing, Smell, Taste

Vestibular Sense:

detects balance and spatial orientation 

Somatic-sensation:

senses from the body, touch, body position, vibration, pain, etc.

Automatic Functions:

functions that do not require conscious thought, reflex circulation, respiration, digestion, etc. 

Higher Functions:

performed by specific areas of the brain only

Cognition:

mental processes such as thinking, learning, memory, language, and executive functions

Emotions:

internal experiences of feelings like happiness, anger, fear, etc. along with physiological responses such as hormone levels and heart rate

Consciousness:

awareness of self, environment, and thoughts

Syndrome:

a recognizable pattern of abnormal functions in the nervous system, often caused by a disease

Somatic Nervous System:

the branch of the nervous system responsible for voluntary control skeletal muscles, enables conscious movement

Acetylcholine/ Somatic (Ach) :

chemical messenger that stimulates skeletal muscle contraction

Autonomic Nervous System:

controls involuntary body functions, branches into the sympathetic nervous system and the parasympathetic nervous system

Sympathetic Nervous System:

short preganglia axon to the ganglia near the spinal card and long postganglia axon to the target cell

Sympathetic Neurons:

short preganglia axon to the ganglia near the spinal card and long postganglia axon to the target cell

Sympathetic Ganglia:

ganglia often linked in a sympathetic chain

Norepinephrine (NE):

a chemical messenger that stimulates alertness and action

Adrenaline:

epinephrine, hormone released by adrenal glands to increase blood constriction 

Parasympathetic Nervous System:

calms the body down after stress and supports routine maintenance

Blood Flow Response–

SNS decreases to intestines and increases to skeletal muscles 

PNS increases to intestines and decreases to skeletal muscles

Heart Output Response–

SNS increases with more blood pumped 

PNS decreases with energy conservation

Gland Response–

SNS activates sweat glands 

PNS activates salivary glands

Acetylcholine/Parasym (Ach):

chemical messenger that promotes relaxation and digestion 

Motor Unit:

consists of one efferent lower motor neuron and all skeletal fibers it innervates

Neuromuscular Junction:

a specialized synapse between a lower motor neuron and a skeletal muscle cell

Small motor unit:

controls fine, precise movements

Large motor unit:

control powerful, less precise movements

Lower Motor Neuron Dysfunction Signs:

clinical signs that suggest damage to the lower motor neurons, atrophy, fasciculations, hypotonia, and hyporeflexia

Atrophy:

muscle shrinks due to lack of stimulation

Fasciculations:

involuntary muscle twitches

Hypotonia:

decreased muscle tone

Hyporeflexia:

decreased muscle stretch reflexes

Reflex:

an involuntary, nearly instantaneous response to a stimulus 

Afferent Limb:

brings sensory information into the CNS

Efferent Limb:

sends motor commands out from the CNS to cause a response

Muscle Stretch Reflex:

a simple, protective mechanism, spinal reflex that contracts a muscle in response to it being rapidly stretched

Reflex Arc Pathway (Stretch)

1. Stimulus- a physical stimulus hits the skin inducing an 

action from the muscles, a stretch in the quadriceps muscle

2. Receptor- specialized stretch receptors inside the 

skeletal muscles detect a rapid stretch and send signals 

through sensory axons 

3. Afferent Neurons- somatosensory neurons carry the stretch 

Signal into the spinal cord via the dorsal root ganglion 

4. Synapse- the afferent neurons forms an excitatory synapse with a lower motor neuron in the spinal cord 

5. Efferent Neurons- the lower motor neurons send a signal back to the same muscle that was stretched, inducing a contraction 

Reciprocal Inhibition:

an inhibitory interneuron is excited by the afferent neuron and inhibits lower motor function from the opposing muscle, to prevent resistance from the efferent signal

Muscle Spindle:

a sensory receptor that is in the skeletal muscle

Monosynaptic Reflex:

a reflex pathway that only involves one synapse in between sensory and motor neuron

Polysynaptic Reflex:

a reflex pathway that involves multiple synapses and interneurons

Lower Motor Neurons:

motor neurons with the soma in the brainstem or spinal cords that have axons that go to skeletal muscles

Higher Motor Neurons:

motor neurons with the soma in the cerebral cortex with axons that travel to the brainstem or spinal cords

Upper Motor Neuron Dysfunction signs:

Hyperreflexia, clonus, hypertonia, and extensor plantar response

Hyperreflexia:

increased muscle stretch due to reflexes

Clonus:

rhythmic, involuntary contractions of antagonist muscles triggered by 

a sudden stretch

Hypertonia:

increased muscle tone stiffness, resistance to passive movement

Extensor Plantar Response:

the abnormal extending of toes when the foot is 

stimulated

Corticospinal Tract:

the controlling of the limb and trunk muscles from the 

cerebral cortex to the spinal cord via axons that cross the medulla

Corticospinal Pathway

1. Axon travels from the motor cortex through the brain 

(internal capsule→ midbrain→ pons→ medulla)

2. Axons cross over in the medulla to the opposite side

3. Axons continue down the spinal cord 

4. Synapse on lower motor neurons in the anterior horn of the spinal cord 

5. Lower motor neurons send signals up the limb and trunk muscles

Corticobulbar Tract:

controls the head/neck muscles from the cerebral cortex to 

the brainstem via bilateral input from axons and  cranial nerves

Corticobulbar Pathway

1. Axons descend from the motor cortex through the internal capsule to the brainstem

2. Synapse on cranial nerve motor nuclei 

3. Nuclei contain LMNs that send signals to the muscles in the face/ head 

Neuron:

a nerve cell that processes and sends electrical signals 

Neurites:

any projection from the neuron–either a dendrite or an axon

Dendrites:

short branches that receive input from other cells

Axon:

long projection that sends signals away from the neuron to other 

cells