MCAT: Organ Systems

parts of the nervous system

central and peripheral

central nervous system

brain and spinal cord

peripheral nervous system

nerves and ganglia

ganglia

clusters of cell bodies in the PNS

cerebral hemispheres

The right and left halves of the cerebrum

cerebrum

Area of the brain responsible for all voluntary activities of the body

afferent neurons

Nerve cells that carry impulses towards the central nervous system

efferent neurons

Nerve cells that conduct impulses away from the central nervous system

midbrain

A small part of the brain above the pons that integrates sensory information and relays it upward.

pons

A brain structure that relays information from the cerebellum to the rest of the brain

medulla

the base of the brainstem; controls heartbeat and breathing

cerebellum

A large structure of the hindbrain that controls fine motor skills.

hindbrain

medulla, pons, cerebellum

forebrain

The largest and most complicated region of the brain, including the thalamus, hypothalamus, limbic system, and cerebrum.

thalamus

the brain's sensory switchboard, located on top of the brainstem; it directs messages to the sensory receiving areas in the cortex and transmits replies to the cerebellum and medulla

hypothalamus

A neural structure lying below the thalamus; it directs several maintenance activities (eating, drinking, body temperature), helps govern the endocrine system via the pituitary gland, and is linked to emotion and reward.

limbic system

neural system located below the cerebral hemispheres; associated with emotions and drives

cranial nerves

12 pairs of nerves that carry messages to and from the brain

spinal nerves

31 pairs of nerves arising from the spinal cord

basic functions of the nervous systems

motor control, sensory detection, automatic responses

syndromes

patterns of nervous system abnormalities

higher functions of the nervous systems

cognition, emotions, and consciousness

motor functions

Complex muscle-and-nerve acts that produce movement (walking, writing, typing running etc.)

sensory functions

sending and processing sensory info. ( hearing, seeing, touch,etc)

automatic responses

things that don't require conscious involvement, like reflexes, respiration, circulation, digestion

cognition

the thinking functions of the brain, learning, language, memory, executive functions

emotions

feelings created in response to thoughts, remarks, and events

consciousness

our awareness of ourselves and our environment

somatosensory tracts

position, vibration, fine touch, pain, temperature, and gross touch

position sense

awareness of static position

vibration sense

subclass of tactile sense, sensed by deformation of tactile receptors

fine touch sense

provides specific information about a touch sensation, such as exactly what point on the body is touched plus the shape, size, and texture of the source of stimulation

pain sense

activated by any factor that damages the tissues

temperature sense

sense hot and cold

gross touch sense

non-localizable

autonomic nervous system

A subdivision of the peripheral nervous system. Controls involuntary activity of visceral muscles and internal organs and glands.

somatic nervous system

the division of the peripheral nervous system that controls the body's skeletal muscles

Sympathetic Nervous System (SNS)

The component of the autonomic nervous system that responds to stressful situations by initiating the fight-or-flight response.

-norepinephrine

parasympathetic nervous system

the division of the autonomic nervous system that calms the body, conserving its energy

-also uses acetylcholine

Acetylcholine (ACh)

A neurotransmitter that enables learning and memory and also triggers muscle contraction; somatic nervous system

motor unit

A motor neuron and all of the muscle fibers it innervates

lower motor neurons

axons leave the CNS, extend through PNS to skeletal muscles. Cell bodies in anterior horns of spinal cord and in cranial nerve nuclei of brainstem

neuromuscular junction

point of contact between a motor neuron and a skeletal muscle cell

atrophy

(n.) the wasting away of a body organ or tissue; any progressive decline or failure; (v.) to waste away

fasciculations

Involuntary contractions or twitchings of muscle fibers

hypotonia

a condition in which there is diminished tone of the skeletal muscles

hyporeflexia

absence of a reflex

muscle stretch reflex

causes a muscle to contact after it's stretched, as a protective response; rubber hammer hitting knee

Upper motor neurons

motor neurons in the central nervous system that control the lower motor neurons in the peripheral nervous system; somas found in cerebral cortex

corticospinal tract

connections between brain and spine

tract

collection of axons in CNS

corticobulbar tract

Controls all voluntary movement for speech production. Descends from motor cortex through internal capsule but terminates at cranial nerves.

upper motor neuron signs

hyperreflexia, clonis, hypertonia, extensor plantar response

Hyperreflexia

Exaggerated reflex response

lower motor neuron signs

atrophy, fasciculations, hypotonia, hyporeflexia

clonis

The rapid repetitive response to stretch.

hypertonia

increased muscle tone

Extensor Plantar Response

if you take a hard object and scrape along bottom of foot, normal response is flexor - toes will come down on the object. But with extensor, toes extend up.

Autonomic Nervous System

the part of the peripheral nervous system that controls the glands and the muscles of the internal organs (such as the heart). Its sympathetic division arouses; its parasympathetic division calms.

- efferent neurons

-smooth muscle

-cardiac muscle

-gland cells

ganglia

clusters of cell bodies in the PNS

forebrain

The largest and most complicated region of the brain, including the thalamus, hypothalamus, limbic system, and cerebrum.

pituitary gland

The endocrine system's most influential gland. Under the influence of the hypothalamus, the pituitary regulates growth and controls other endocrine glands.

forebrain function

thinking, sensing,memory, emotions, hunger, sleep, fullness

hindbrain functions

balance, motor coordination, breathing, digestion, general arousal processes (sleeping and waking); "vital functioning"

neural cells

neurons and neuroglia

neurons

a nerve cell; the basic building block of the nervous system

neuroglia

cells that support and protect neurons

neuron structure

cell body/soma, dendrites, axon, myelin sheath

myelin sheath function

Protect and electrically insulate the axon

Increase speed of nerve impulse transmission

node of Ranvier

A gap between successive segments of the myelin sheath where the axon membrane is exposed.

synapse

the junction between the axon tip of the sending neuron and the dendrite or cell body of the receiving neuron

unipolar neuron

a neuron with one process extending from its cell body

bipolar neuron

a neuron with one axon and one dendrite attached to its soma

multipolar neuron

A neuron with a single axon and multiple dendrites; the most common type of neuron in the nervous system.

pseudo-unipolar neuron

One axon that splits into two branches

Sensory neurons

neuron function

Neurons are highly irritable

Respond to adequate stimulus by generating an action potential (nerve impulse)

Impulse is always the same regardless of stimulus

resting membrane potential

the electrical charge of a neuron when it is not active

action potential

a neural impulse; a brief electrical charge that travels down an axon

graded potential

a shift in the electrical charge in a tiny area of a neuron

threshold potential

The minimum membrane potential that must be reached in order for an action potential to be generated.

interneuron

a neuron that carries nerve impulses from one neuron to another

Astrocytes

Provide structural and metabolic support for neurons; they migrate to areas of injury and wall off the area almost like a "scar"; astrogliosis/glial scar; homeostasis; blood-brain barrier

"star cells"

- end feet

Microglia

phagocytic cells that ingest and break down waste products and pathogens in the CNS; turn into blob and look for bacteria/etc., kill it, ingest the debris (phagocytosis); antigen presentation

antigen presentation

the display of the antigen fragment in an exposed groove of the MHC protein

ependymal cells

line cavities of the brain and spinal cord, circulate cerebrospinal fluid; microvilli and cilia;

Oligodendrocytes

Type of glial cell in the CNS that wrap axons in a myelin sheath.

Schwann cells

Supporting cells of the peripheral nervous system responsible for the formation of myelin.

sodium-potassium pump

a carrier protein that uses ATP to actively transport sodium ions out of a cell and potassium ions into the cell

ion leak channels

allow ions to cross the plasma membrane down their electrochemical gradient

Chloride Potassium Symporter

Integral membrane protein that uses potassium leaving cell to push out chloride

action potential figure

saltatory conduction

sending a message in a myelinated neuron, the impulse jumps from node to node

hyperpolarization

The movement of the membrane potential of a cell away from rest potential in a more negative direction.

repolarization

Return of the cell to resting state, caused by reentry of potassium into the cell while sodium exits the cell.

refractory period

a period of inactivity after a neuron has fired

axon diameter

the larger the diameter, the faster the impulse because it offers less resistance; higher probability that the ions will travel further before colliding into things

proprioception

our sense of body position; very fast acting nerves

conduction velocity

the speed at which an action potential is propagated along the length of an axon

synaptic cleft

The narrow gap that separates the presynaptic neuron from the postsynaptic cell.

pre-synaptic cell

The cell SENDING information (from axon); where the NTs are stored