Nervous System

Functions of the nervous system

Sensory input, integration, motor output

Sensory (afferent) neurons

Carry information to the CNS.

Motor (efferent) neurons

Carry commands from the CNS to muscles/glands.

Interneurons

Connect sensory and motor neurons inside the CNS.

CNS components

Brain and spinal cord.

PNS components

Cranial nerves, spinal nerves, ganglia, peripheral nerves.

Number of cranial nerves

12 pairs.

Number of spinal nerves

31 pairs.

Synapse

Junction where a neuron communicates with another cell using neurotransmitters.

White matter

Myelinated axons.

Gray matter

Neuron cell bodies, dendrites, unmyelinated axons.

CNS neuroglia

Astrocytes, oligodendrocytes, microglia, ependymal cells

PNS neuroglia

Schwann cells and satellite cells.

Astrocytes

Form blood-brain barrier; support neurons.

Oligodendrocytes

Form myelin in CNS

Microglia

Immune cells of CNS; phagocytosis

Ependymal cells

Produce and circulate CSF

Schwann cells

Form myelin in PNS

Satellite cells

Support neuron cell bodies in ganglia

Subdivisions of the PNS

Somatic, autonomic

Sympathetic division

Fight or flight.

Parasympathetic division

Rest and digest

Meninges layers (superficial to deep)

Dura mater → Arachnoid mater → Pia mater

Subarachnoid space

Contains CSF

Cervical enlargement

Nerves to upper limbs

Lumbar enlargement

Nerves to lower limbs

Conus medullaris

End of spinal cord (L1–L2)

Cauda equina

Bundle of nerve roots below the conus

Filum terminale

Connective tissue that anchors spinal cord

Denticulate ligaments

Lateral stabilizers of spinal cord (from pia mater)

Epidural anesthesia

Injection into epidural space outside dura

Lumbar puncture

CSF removal from subarachnoid space below L2

Dermatome

Skin area supplied by one spinal nerve

Fast, automatic, involuntary response

Reflex

Receptor → Sensory neuron → Integration → Motor neuron → Effector

Reflex arc components

Controls heart rate, breathing, blood pressure

Medulla oblongata function

Breathing rhythm; connects cerebellum to brain

Pons function

Balance, coordination, motor learning

Cerebellum function

Thalamus function

Relay station for sensory information

Hypothalamus function

Homeostasis; temperature, hunger, hormones

Thought, memory, voluntary movement

Cerebrum function

Internal carotid arteries and vertebral arteries

Blood supply TO brain

Dural venous sinuses → internal jugular veins

Blood drainage from brain

protecting the brain by regulating molecule and ion flow between blood and brain tissue, acting like a "bouncer" to let vital nutrients (like glucose) in while blocking toxins, pathogens, and waste

Blood-brain barrier function (BBB)

CSF functions

Cushioning, buoyancy, nutrient/waste transport

CSF is produced by

Choroid plexus (ependymal cells)

Smell — Sensory.

Cranial Nerve I — Olfactory

Vision — Sensory

Cranial Nerve II — Optic

Eye movement — motor

Cranial Nerve III — Oculomotor

Eye movement (superior oblique) — Motor

Cranial Nerve IV — Trochlear

Face sensation & chewing — Both

Cranial Nerve V — Trigeminal

Eye movement (lateral rectus) — Motor

Cranial Nerve VI — Abducens

Facial expression, taste (front 2/3 tongue), tears/saliva — Both

Cranial Nerve VII — Facial

Hearing & balance — Sensory

Cranial Nerve VIII — Vestibulocochlear

Taste (posterior 1/3), swallowing, salivation — Both

Cranial Nerve IX — Glossopharyngeal

Parasympathetic control of heart, lungs, digestive organs — Both

Cranial Nerve X — Vagus

Controls sternocleidomastoid & trapezius — Motor

Cranial Nerve XI — Accessory

Tongue movement — Motor

Cranial Nerve XII — Hypoglossal

Which division of the nervous system carries signals away from the CNS to muscles and glands?

C. Efferent division

Which part of the neuron conducts action potentials toward the cell body?

dendrites

The functional unit of the nervous system is the

neuron

The synapse is best defined as

A junction where a neuron communicates with another cell

Schwann cells myelinate axons in the

PNS

Which structure anchors the spinal cord laterally and prevents side-to-side movement?

Denticulate ligament

A lumbar puncture is usually performed between

L3–L4 or L4–L5

The conus medullaris ends at approximately

L1-L2

The blood–brain barrier is primarily maintained by

astrocytes

Which cranial nerves are sensory only

I, II, VIII

What structure separates the cerebrum from the cerebellum

Transverse fissure / tentorium cerebelli

Which neuroglial cell would increase in number during a brain infection caused by bacteria?

Microglia

Which structure allows CSF to drain from the subarachnoid space into the venous system?

Arachnoid villi

Damage to the dorsal horn of the spinal cord would result in loss of

Sensory function

Which layer of meninges contains blood vessels that directly supply the brain tissue?

Pia mater

Which brain region would be affected if a patient has difficulty maintaining posture and performing smooth coordinated movements?

Cerebellum

Which part of the spinal cord contains autonomic motor neurons?

Lateral hornn

Which cranial nerve emerges from the brainstem but ALSO receives spinal rootlets from the cervical region?

Accessory

Which of the following is TRUE about the blood–brain barrier (BBB)?

It is formed by endothelial cells joined by tight junctions

Which structure produces MOST of the CSF?

Lateral ventricles (because the choroid plexus is largest there)

Which division of the PNS brings signals from internal organs to the CNS?

Visceral sensory

Which space is used for delivering epidural anesthesia?

Epidural

Which subdivision of the PNS controls skeletal muscles?

Somatic motor

A patient has droopy eyelids, cannot move eyes up/down, and has dilated pupils. What nerve is damaged?

Oculomotor (III)

A tumor compresses the arachnoid mater preventing CSF flow. What happens?

Increased intracranial pressure → hydrocephalus → headaches & vomiting

Which structures are made of gray matter?

Dorsal horn, Ventral horn, Lateral horn

Which meningeal layers are separated by actual spaces?

Subarachnoid space, Epidural space

Which belong to the autonomic nervous system?

Sweat glands

Heart muscle
Smooth muscle

Which nerves are both sensory and motor?

V

VII

IX

X

What is the minimum number of neurons in a reflex arc?

2

Which glial cell cleans up debris and acts like a macrophage?

Microglia

A patient cannot move their tongue properly. Which nerve is damaged?

XII

Which cranial nerves carry taste information?

VII

IX

X