Nervous System

Functions of the nervous system

Receive sensory input from internal and external environments: Ex. pressure, taste, sound, light, blood pH, hormone levels- converted to a signal and sent to the brain or spinal cord
Integrate the input: In the sensory centers of the brain or spinal cord, the barrage of input is integrated and a response is generated
Respond to stimuli: The response, a motor output, is a signal transmitted to organs that then can convert the signal into some form of action
Ex. movement, changes in heart rate, release of hormones

Central nervous system

brain and spinal cord

Peripheral nervous system

nerves that connect the brain and spinal cord to the rest of the body, carries nerve impulses sent between CNS and the rest of the body.
Ex. sensory neurons, motor neurons, somatic nervous system, autonomic nervous system, cranial nerves, spinal nerves

Brain's three major parts

cerebrum, cerebellum, brain stem

Hypothalamus

controls temperature and appetite

Cerebrum

largest part of the brain, contains the parietaI, frontal, temporal, and occipital
It is divided into 2 hemispheres by longitudinal fissure
Rt. hemisphere is creative side, controlling artistic ability and emotions
The left hemisphere contains centers for speech, thinking, voluntary movement, reading, writing, hearing, vision, and motor action
Corpus callosum (white matter) connects right and left hemispheres
Cerebral surface: covered in ridges (gyri) and grooves (sulci)
Outer layer: cerebral cortex (gray matter)
Cerebrum divided from cerebellum by transverse fissure

Cerebellum

(little brain) essential for coordination of voluntary movement
Maintaining balance
Coordination of eye movements
Holds more than ½ of neurons of entire body

Brain stem

Relay center connecting cerebellum and cerebrum to spinal cord
Performs many autonomic features breathing, heart rate, digestion, sneezing, coughing, swallowing
10 of 12 cranial nerves emerge from brainstem
Contains the midbrain, pons, and medulla oblongata

Midbrain

associated with vision, hearing, motor, control, sleep wake cycles, alertness, and T regulation
Relays sensory and motor info

Pons

relays sensory and motor info from forebrain to cerebellum, role in sleep, respiration, swallowing, bladder control, hearing, equilibrium, taste, eye movement, facial expressions, facial sensation and posture

Medulla oblongata

lower half of brain stem
Vital functions cardiac, respiratory, vomiting, and vasomotor centers
Regulates autonomic, involuntary functions like breathing, heart rate, and blood pressure

Spinal cord

Cable of nerve tissue extends from medulla oblongata to lumbar region of vertebral column
Nerve impulses from body and brain run up and down
Reflexes
Surrounded and protected by vertebrae

Meninges

3 membranes lining skull and vertebral canal enclose the brain and spinal cord- sterile atmosphere
Brain/spinal cord surrounded by meninges for protection
Act as cushions and shock absorbers
Dura mater, Arachnoid mater, Pia mater

Dura mater

thick, outermost layer of the meninges surrounding and protecting the brain and spinal cord

Arachnoid mater

middle layer of the meninges

Pia mater

thin, delicate inner membrane of the meninges

Cerebral spinal fluid

clear liquid that bathes brain/spinal cord
Subarachnoid space between arachnoid and pia
Contains glucose, protein, H2O
Acts as a shock absorber

Cranial nerves

They extend from out the brain
12 pairs- designated by name and number
Connect the brain to the head (functionally)
Most carry both sensory and motor fibers

Olfactory I

sensory neuron, smell

Optic II

sensory neuron, vision

Oculomotor III

motor neuron, most eye movement

Trochlear IV

motor neuron, moves eye

Trigeminal V

sensory and motor neuron, face sensation, mastication

Abducens VI

motor neuron, abducts the eye

Facial VII

sensory and motor neuron, facial expression, taste

Vestibulocochlear VIII

sensory neuron, hearing, balance

Glossopharyngeal IX

sensory and motor neuron, taste, gag reflex

Vagus X

sensory and motor neuron, gag reflex, parasympathetic innervation

Accessory XI

motor neuron, shoulder shrug

Hypoglossal XII

motor neuron, swallowing, speech

Spinal nerves

31 pairs of peripheral nerves- contain both sensory and motor fibers
8 pairs cervical
12 pairs thoracic
5 lumbar
5 pairs sacral
1 coccygeal

Sensory neurons

Carry nerve impulses from sense organs and receptors to the CNS, also called afferent neurons

Motor neurons

Carry impulses from CNS to the muscles and glands
Also called efferent neurons
contains somatic and autonomic

Interneurons

conduct impulses from sensory neurons to motor neurons, also called central or connecting neurons

Somatic nervous system

controls skeletal muscle and voluntary movements

Autonomic nervous system

organs, controls smooth and cardiac muscle and several glands, systems are involuntary
Ex. heartbeat, breathing
contains sympathetic and parasympathetic

Sympathetic

body's accelerator triggered by alarm state, "fight or flight", all voluntary systems (mainly muscles)

Parasympathetic

body's brake triggered by relaxation, organs and systems not under voluntary control, Ex. rest or digest

Neuron

transmitting a message from one cell to the next

Synapse

gap between neurons, a junction where information is transmitted from one neuron to the next.

Dendrite

fibers extending from a neuron cell that conduct impulses toward the cell body

Axon

a fiber extending from a neuron cell that conducts impulses away from the cell. Each nerve cell has only one axon

Myelin sheath

a fatty tissue that wraps the axon to protect it and helps speed up impulses as they travel down the axon

Neurotransmitters

Epinephrine
Norepinephrine
Acetylcholine- between muscles and nerve cells

Multiple sclerosis

Myelin destroyed, may involve the axon and cell body- conduction slow or impossible
Usually involves brain, spinal cord, and optic nerves
Symptoms differ depending on where the myelin damage occurs
Causes disturbances in vision, balance, speech or movement
No cure, medications can slow progression, learn to manage symptoms

Cerebrovascular accident

Stroke
Brain tissue dies
Symptoms sudden and many are permanent
Can be due to bleeding in the brain (hemorrhagic) or disruption of blood flow (ischemic)
Sensory, language, motor and/or memory difficulties

Alzheimer's disease

progressive, cause not fully known
Begins with difficulty remembering recently learned info (short term memory loss)
Believed to be a build up of plaque (destruction of nerve endings in the cortex that block signals between nerve cells), and a defect in the neurotransmitters

Myasthenia gravis

a chronic autoimmune disease that affects the neuromuscular junction and produces serious weakness of voluntary muscles

Traumatic brain injuries

Force applied to the skull, causing damage to the brain tissue
Closed-: skull not open
Penetrating: skull punctured
Concussion: a more mild brain injury
Contusion: more serious, characterized by swelling and/or bleeding

Autism

A developmental disorder marked by disabilities in language, social interaction, and the ability to understand another person's state of mind

Meningitis

an infection of the meninges, causing inflammation of the meninges
Bacterial: IV antibiotics, if untreated can cause seizures, coma, amputation of limbs, or death
Viral: bed rest, fluids, medications to relieve symptoms

Amyotrophic Lateral Sclerosis

Muscle weakness, twitching and cramping, progresses to complete paralysis, difficult speaking and swallowing, diaphragm paralyzed
Motor neurons in cerebral cortex, brain stem, and spinal cord self-destruct