MCAT BIOLOGY

Central Nervous System (CNS)

integrates information and coordinates responses

brain and spinal cord

Peripheral nervous system (PNS)

peripheral nerves and ganglia

Afferent neurson

carry sensory info towards CNS

Efferent neurons

carries motor commands away from the CNS to muscles and glands

somatic nervous system

skeletal muscles, voluntary movements, reflexes

autonomic nervous system

smooth/cardiac muscle, glands, involuntary movements

sympathetic nervous system

fight or flight, increases blood flow to active muscles

parasympathetic nervous system

rest and digest

Heart rate

sympathetic: increases

parasympathetic: decreases

Pupils

Sympathetic: dilate

Parasympathetic: constrict

Airways

Sympathetic: dilate

Parasympathetic: constrict towards resting levels

Digestion

Sympathetic: Decreases digestive activity

Parasympathetic: Increases digestive activity and peristalsis

Energy availability

Sympathetic: mobilizes fuel, increasing blood glucose

Parasympathetic: favors digestion and energy storage

neuron

receives and transmits information

Dendrites

receives incoming signals

cell body (soma)

maintains the cell and integrates the inputs

axon

carries action potentials toward the axon terminals

Glial cells

support neurons

myelin

insulating sheath around axons

oligodendrocytes

make myelin in the CNS

schwann cells

make myelin in the PNS

nodes of ranvier

allow action potentials to regenerate along the axon

saltatory conduction

speeds signaling

gray matter

important for processing information

white matter

connects regions through myelinated matter

Depolarization

makes membrane potential less negative

Hyperpolarization

makes the membrane potential more negative

when does an action potential begin

when depolarization reaches a threshold

what causes the membrane to repolarize

inactivation of sodium channels and potassium exits through voltage-gated potassium channels

what does a stronger stimulus affect

firing frequency NOT a taller action potential

refractory period

limits how soon a neuron can fire again

synaptic cleft

neurotransmitters are released to transmit nerve impulses

Excitatory postsynaptic potential (EPSP)

makes an action potential more likely by depolarizing the cell

Inhibitory postsynaptic potential (IPSP)

makes an action potential less likely by hyperpolarizing the cell

Temporal summation

combines inputs arriving rapidly from the same source

Spatial Summation

combines inputs arriving from different sources

spinal cord

carries information between the brain and the body

reflexes

automatic responses to a stimulus

dorsal roots

sensory fibers enter through

Ventral roots

motor fibers leave through

Interneurons

connect neurons with the CNS

monosynaptic relfex

synapse between a sensory and motor neuron, knee-jerk reflex

polysynaptic reflex

one or more interneurons

Ascending pathways

carry sensory info towards the brain

descending pathways

carry motor commands from the brain to the body

forebrain

cerebrum, thalamus, and hypothalamus

complex thought, sensory processing, memory, emotion, and homeostasis

Midbrain

movement, arousal, reward

Hindbrain

induces: pons, medulla, and cerebellum

supports vital functions and movement coordination

brainstem

consists of midbrain, pons, and medulla

cerebral cortex

outer gray matter of the cerebrum, four main lobes

prefrontal cortex (frontal)

planning, judgement, working memory, impulse control, and social behavior

Primary motor cortex (frontal)

voluntary movement

Broca’s area (frontal)

speech production, left hemisphere

parietal (primary somatosensory complex)

somatosensation, integration of sensory information, and spatial processing

Temporal (wernicke’s area)

hearing, memory functions, language comprehension, and contains auditory cortex on the left.

Occipital

visual processing (color, form, and motion)

contralateral

each hemisphere controls/receives info from the opposite side

thalamus

relays sensory information to the cortex, olfaction is the exception

hypothalamus

regulates homeostasis (hunger, thirst, temperature, sexual behavior, and autonomic and endocrine activity)

suprachiasmatic nucleus (SCN)

coordinates circadian rhythms

hippocampus

form and consolidate new memories

amygdala

emotional processing (fear and threat)

limbic system

hippocampus, amygdala, hypothalamus

basal ganglia

selects and initiates movements and procedural learning

nucleus accumbens

reward and reinforcement

substantia nigra

dopamine to motor circuits in basal ganglia

ventral tegmental area (VTA)

dopamine to reward and motivation circuits, nucleus accumbens

reticular formation

supports arousal and attention, helps to maintain wakefulness

pons

relays info, sleep and breathing regulation

medulla

vital functions (breathing, heart rate, blood pressure)

cerebellum

movement, balance, posture, motor learning, and precise timing

lateralization

some functions rely more heavily on one hemisphere

left hemisphere

language

right hemisphere

visuospatial processing, music perception, and emotional tone of speech

corpus callosum

connects the hemispheres

left visual field

right hemisphere

right visual field

left hemisphere

structural methods

show anatomy of the brain

functional methods

measure activity of processes in the brain

CT (CAT)

X-ray to show structure

MRI

magnetic fields and radiowaves to show structure

fMRI

uses changes in blood oxygenation to locate activity indirectly

PET

uses radioactive tracers to measure processes

EEG

records electrical activity at the scalp, good for timing bad for location

MEG

records magnetic fields produced by neural activity, great with timing

lesion studies

examine changes after brain damage in a region

electrical stimulation and transcranial magnetic stimulation (TMS)

change activity to investigate a regions function

glutamate

major excitatory transmitter in the CNS, learning and memory

GABA

major inhibitory transmitter in the brain, reduces neural excitability

Glycine

important inhibitory transmitter in the spinal cord and brain stem

dopamine

movement, reward, motivation, and reinforcement. Effects depend on pathway

serotonin

mood, sleep, appetite, and regulation of impulsitivity and aggression

Norepinephrine

alertness, attention, and sympathetic responses

epinephrine

adrenal hormone in the fight or flight response

acetylcholine (ACh)

skeletal muscle contraction, autonomic signaling, attention, memory

endorphins

reduce pain signaling and influence reward