BIO 417 Exam 3

Nervous system

Body-wide network that gathers sensory info, processes it in the brain/spinal cord, and sends motor output

Central nervous system

Brain + spinal cord — integrates and processes all information

Peripheral nervous system

Nerves outside CNS linking brain/spinal cord to organs, skin, and muscles

Afferent axons

Carry sensory info to CNS

Efferent axons

Carry motor commands from CNS

Somatic nervous system

Voluntary division controlling skeletal muscles and external senses

Autonomic (visceral) system

Involuntary division regulating heart, smooth muscle, and glands

Rostral

Toward the front or nose

Caudal

Toward the tail or back end

Dorsal

Toward the back/top of brain

Ventral

Toward the belly or underside

Medial

Toward midline

Lateral

Away from midline

Ipsilateral

On the same side of the body

Contralateral

On the opposite side of the body

Cerebrum

Largest brain part — thought, memory, emotion, voluntary control

Cerebellum

Behind brainstem — balance, coordination, fine-tuning movement

Brainstem

Connects brain ↔ spinal cord; controls heart rate, breathing, alertness

Spinal cord

Conduit for ascending sensory and descending motor signals

Dorsal root

Brings sensory input into spinal cord

Ventral root

Sends motor output from spinal cord to muscles

Dorsal root ganglia

Sensory neuron cell bodies just outside spinal cord

Cranial nerves

12 nerve pairs from brainstem — mostly head and neck sensation/movement

Meninges

Three membranes (dura, arachnoid, pia) that protect brain and cord

Dura mater

Thick outer protective layer

Arachnoid mater

Middle "web-like" layer

Pia mater

Thin inner layer hugging brain surface

Subarachnoid space

Between arachnoid and pia; contains cerebrospinal fluid

Cerebrospinal fluid

Clear fluid cushioning brain, circulating nutrients and waste

Ventricles

CSF-filled cavities inside brain

Choroid plexus

Tissue in ventricles that makes CSF

Arachnoid villi

Drain CSF back into bloodstream

Neural plate

Flat ectodermal sheet that forms the nervous system

Neural groove

Midline depression in plate during development

Neural tube

Closed structure that becomes brain + spinal cord

Neural crest

Edge cells that form PNS neurons and other tissues

Somites

Segmented mesoderm forming vertebrae and skeletal muscle

Anencephaly

Anterior neural tube fails to close → missing forebrain

Spina bifida

Posterior neural tube fails to close → exposed spinal tissue

Prosencephalon

Forebrain → telencephalon + diencephalon

Mesencephalon

Midbrain → tectum + tegmentum

Rhombencephalon

Hindbrain → pons + cerebellum + medulla

Telencephalon

Forms cerebral cortex, basal ganglia, olfactory bulbs

Diencephalon

Forms thalamus and hypothalamus

Thalamus

Major relay sending sensory/motor signals to cortex

Hypothalamus

Regulates hunger, temp, hormones, circadian rhythm, autonomic control

Basal ganglia

Subcortical nuclei that start and regulate movement patterns

Caudate nucleus

Movement learning + feedback processing

Putamen

Helps control repetitive and learned movements

Globus pallidus

Adjusts posture and muscle tone

Olfactory bulbs

Forebrain structures for smell processing

Corpus callosum

White-matter bridge connecting hemispheres

Internal capsule

Fiber pathway linking cortex ↔ brainstem/spinal cord

Cortical white matter

Axon tracts interconnecting cortical neurons

Tectum

Dorsal midbrain — superior + inferior colliculi

Superior colliculus

Visual reflex center for eye/head tracking

Inferior colliculus

Auditory relay to thalamus

Tegmentum

Ventral midbrain — red nucleus + substantia nigra for movement control

Substantia nigra

Dopamine center — damaged in Parkinson's

Red nucleus

Motor coordination relay from cerebellum

Cerebellum

Controls precision and timing of movements, posture, and balance

Pons

Connects cerebrum↔cerebellum; coordinates movement intent

Medulla oblongata

Controls breathing, heart rate, basic reflexes

Gray matter

Neuron cell bodies; integration and local processing

White matter

Myelinated axons; long-distance communication

Dorsal horn

Receives sensory input in spinal cord

Ventral horn

Houses motor neurons projecting to muscles

Intermediate zone

Interneurons linking sensory and motor circuits

Dorsal column

Ascending tract for touch + proprioception

Lateral column

Descending motor and autonomic tracts

Corticospinal tract

Motor pathway cortex→spinal cord for voluntary movement

Gyri

Cortical ridges increasing surface area

Sulci

Grooves separating gyri

Cerebral cortex

Six-layer sheet handling perception, thought, and voluntary motion

Brodmann areas

Numbered cortical regions by cell pattern/function

Primary sensory cortex

First cortical stop for each sensory pathway

Secondary sensory cortex

Integrates and interprets sensory input

Motor cortex

Origin of voluntary motor commands

Area 17

Primary visual cortex — damage = blindness

Area 4

Primary motor cortex — controls opposite-side body

Neocortex

Six-layered "new" cortex for complex cognition

Limbic system

Emotion, motivation, and memory network

CSF flow

Lateral → third → fourth → subarachnoid space

Blood-brain barrier

Selective filter shielding brain from toxins

Synapse

Junction where neurons communicate chemically

Neurotransmitter

Chemical signal crossing synapse

Glutamate

Main excitatory transmitter

GABA

Main inhibitory transmitter

Acetylcholine

At neuromuscular junction + autonomic synapses

Dopamine

Controls reward + movement

Serotonin

Mood, appetite, sleep regulator

Norepinephrine

Alertness + sympathetic tone

Myelin

Fatty sheath speeding impulse conduction

Node of Ranvier

Gap enabling saltatory conduction

Astrocyte

Maintains ion balance, supports neurons

Oligodendrocyte

Myelin in CNS

Schwann cell

Myelin in PNS

Microglia

Immune defense + debris cleanup in CNS

Action potential

Brief depolarization spike along axon

Resting potential

Baseline charge (~ -70 mV)