Nervous System

Nervous System

• Monitors changes that occur in the internal and external environment (communicates)

• Processes and interprets to make “decisions”

(integrates)

• Commands responses by activating muscles, glands, and other parts of nervous system

(coordinates)

Sense Integrate Motor

Sensory Function (communication)

• Peripheral nerves

• Detect changes inside & outside of the body

• External stimuli

– light, sound, temperature,

• Internal stimuli

– concentration of oxygen, pH, concentration of carbon dioxide

• Transmitted to CNS

Integrative Function (control)• Receive nerve impulses

from peripheral nerves

• Create sensations

• Conscious/Subconscious decisions are made (acted on by the motor neurons)

Motor Function (coordination)• Act on “decisions” made by sensory and

integrative functions

• Effectors

– outside the nervous system

– muscles

– glands

Central Nervous System (CNS) Peripheral Nervous System (PNS)

• Brain

• Spinal cord

• Peripheral nerves

–Cranial and spinal

Efferent and Afferent Divisions (functional)Afferent division• Sensory info gets transferred from PNS to CNS

Efferent division• Sends out motor commands from PNS to muscles

and glands (effectors)• Divided into…

– Somatic nervous system• Skeletal muscle control

– Autonomic nervous system• Automatic, involuntary control of smooth muscle, cardiac

muscle, and glandular secretions

Structural Classification of NeuronsSpecialized to react to physical and

chemical changes in the environment– Amitotic

• Direct cell division but cannot undergo cell division

• Multipolar

– Many nerve fibers

– One axon; many dendrites

– Within brain and s. cord

• Bipolar

– One dendrite; one axon

– Eyes, nose, ears

• Unipolar

– Found in ganglia

Neuron StructureCell body

• Nissl bodies involved in protein synthesis

• Nucleus (no mitotic division)

• Neurofibrils – fine fibers that extend through neuron to aid impulse transmission

Dendrite

• short, numerous, highly branched

• main receptor surface; receives stimuli and takes to cell body

Neuron StructureAxon

• Carry nerve impulses away to the effectors or other dendrites

• Can have side branches called an axon collateral

• Axon terminals telodendria

Schwann cells

• Around axon to form myelin sheath

• Neurilemma is the outer covering of the schwann cell

Nodes of Ranvier

• Gaps between Schwann cells

• Increases speed of impulse conduction

Myelination• Protein sheath around the axon

• Myelin made by oligodendrocytes

• Stored in the Schwann cells that wrap around the axon

• Referred to as white matter

• Impulses travel quickly & smoothly

• Unmyelinated

– gray matter

– impulses travel slower

– infant brain

• Multiple Sclerosis– Autoimmune

– Demyelination

Functional Classification of Neurons

Sensory

– Afferent

– Associated with a receptor

– Mainly outside CNS

Interneurons

– Totally within the CNS

Motor

– Efferent

– Fires the last impulse

– Mainly outside CNS

Sensory Neurons

• Receive impulses from PNS

• Sent to brain/spinal cord

• Receptor ends

– tips of dendrites

– associate with receptor cells

• Receptor cells

– skin or sensory organs

Interneurons

• Most abundant

• Found within brain & spinal cord

• Redirect sensory impulses to the correct brain location

– processing and interpreting then occur

Motor Neurons

• Carry impulses from brain or spinal cord to effectors

• Effectors

– respond to the stimuli after interpreted by the brain

• Law of One Way Conduction

– Dendrite cell body axon…effector

Neuroglial cells

Provide for physiological needs of neurons

Found between the neurons in the nervous tissue

Capable of cell division

Microglial

• Phagocytize bacteria and cellular debris

Oligodendrocytes

• Occur in rows & produce myelin

• Myelinate short sections of many axons

Neuroglial cellsAstrocytes

• Structural support, join parts through processes, regulate concentration of nutrients/ions between blood and brain

• Can form blood brain barrier

• Form scar tissue when injury occurs to CNS

Ependymal

• Form epithelial like coverings for specialized regions

• May produce CSF

• Ciliated to circulate CSF

Neuroglial cells of PNSSatellite Cells

• Surround and support

• Same as astrocytes of CNS

Schwann Cells

• Cover every axon outside the CNS

• Outer surface is the neurilemma

• Only myelinates only one segment of a single axon

Nerve ImpulsePropagation of action potentials along a nerve fiber

All or none response– if it responds, it does so completely

Saltatory conduction– appearing to jump from node to node– Myelinated

– 120 m/s; 270 mph

Continuous conduction

- Unmyelinated

– impulse over entire surface

– slow and jerky 1 m/s; 2 mph

Cell Membrane Potential

• Surface of cell membrane is polarized

– Negative and positive charges are held apart by the membrane

• Selective channels

– 1. Potassium

– 2. Sodium

– 3. Calcium

• Na-K pump

– Activie

– Maintains the membrane potential

Cell Membrane PotentialResting potential (-70 mV)• lots of Na+ and Cl – in

extracellular fluid• Lots of K+ and negatively

changed proteins inside

Threshold potential (-55 mV)• minimum stimulation

needed

Action potential• permeability of membrane

changes• Na+ in and K+ out

Events Leading to a Nerve ImpulseFiber maintains resting potential

Stimulus

• threshold is reached (-55 mV)

Na channels open

• Na diffuses in

• Membrane is depolarized

Events Leading to a Nerve ImpulseK diffuses out

• Membrane repolarizes

Action potential stimulates membranes

Nerve impulse occurs

• wave of action potentials travel the length of the nerve fiber

Anesthetics• block permeability of Na+ so pain can’t

be sensed

Neuron communication• Synapse

– Junction between two communicating neurons• Synaptic cleft

– gap that separates the neuronsNeurotransmittersExcitatory• increase permeability to cause impulses

• Acetylcholine

– stimulates skeletal muscle contractions

• NorepinephrineInhibitory• decreases permeability inhibiting impulses

• Dopamine

– Opposes acetylcholine to keep skeletal muscle contractions from being jerky

• GlycineRole of enzymes• breakdown neurotransmitters• acetylcholine and cholinesterase

Somatic Nervous System

• Portion of PNS• Controls voluntary

activities• Activation of

skeletal muscles

Autonomic Nervous System

• Portion of PNS• Functions without conscious

effort• Visceral functions• Regulates • Smooth muscles• Heart rate• Blood pressure• Breathing rate • Body temp

• May respond to emotional stress

• Sympathetic division relays to the spinal cord

• Parasympathetic division relays to the brain – specifically the medulla oblongata

Action Potential and Neuromuscular Junction ReviewOpen up the handouts in moodle on the steps of action potential and actions at the neuromuscular junction

Complete both handouts using your notes.

Epilepsy

• Abnormal & excessive discharge of impulses to skeletal muscles– Sodium channels remain open

• Neurotransmitters depleted– Seizure ends

• Monitor using EEG and looking for brain wave activity

• Dilantin– stabilizes Na+ so impulses

aren’t over used

Types of Nerves Sensory

• conduct impulses to the brain

Motor

• carry impulses to the effectors

Mixed

• both sensory and motor functions

• most typical type found

Shingles• Varicella zoster

–Must have had chicken pox to develop shingles

• Inflammation of nerves

• No treatment

Spinal Cord Structure

• Passes from brain through vertebrae

• 31 segments

– cervical, thoracic, lumbar

• Ascending tracts

–body to brain

• Descending tracts

–brain to body

Spinal Cord Functions• Two way communicator

• Conducting nerve impulses

• Center for spinal reflexes

Reflexes

• Automatic, subconscious responses to changes inside/outside the body

• Somatic reflex associated with voluntary activities

– Knee jerk

– Withdrawal

• Autonomic reflex associated with heart, smooth muscle, and glands

Brain Anatomy

Posted on resources pageUse to aid in learning functions

and completing function chart

Brain AnatomyMain divisions• Cerebral

hemispheres• Brain Stem• Cerebellum

Meninges

Cerebrospinal fluid

Empty chambers are referred to as ventricles (filled with CSF)

Cerebrum(gyri vs. sulci)

Olfactory Lobe

Brain StemPons• Relays sensory information

from the medulla to the cerebrum

• Controls rate and depth of breathing

Medulla Oblongata• Control center for visceral

organs• Cardiac, vasomotor, and

respiratory centers Midbrain

Brain Stem

Optic Nerve

Pineal Body

Pineal Body• Gland attached to the

optic nerve• Produces melatonin

which regulates the sleep and wake cycles–Dark triggers

melatonin to be produced which triggers sleep

Thalamus and Hypothalamus

Hippocampus

Hemisphere DominanceDominant hemisphere

controls• speech, writing,

reading• verbal, analytical,

computational skillsNondominant

hemisphere• motor tasks,

interpreting music, nonverbal visuals

• emotional and intuitive thinking

Learning Style and Hem. Dominance Inventories

Exit Slip

Socrative 242221

DisordersConcussion

• Slight and transient brain injury

• caused by blows to the head

• Immediate symptoms can include– amnesia, memory loss, difficulty

concentrating, headache, sensitivity to light and dizziness.

• Delayed symptoms can include– sleep disturbance, fatigue,

depression and fogginess

Contusion

• Traumatic brain injury that destroys brain tissue

Cerebral edema

• Retention of water in the brain

• “swelling”

DisordersHuntington’s

• Dominant gene found on chromosome 4

• Late acting

• Neurons deteriorate; unrestrained movement

Disorders

Whiplash• Damage to cervical nerves

Cerebral palsy• Damage to brain tissue at birth• Permanent, nonprogressive

damage to motor control area

CVA•Stroke•Hemorrhage/cessation of blood flow to the brain•Prolonged exposure to ischemia (decreased blood supply to a body organ)Transient Ischemic attack (TIA)•Mini stroke

Disorders

Meningitis

• Inflammation of meninges

• Bacterial or viral

• Present as flu like symptoms

• Stiff neck and back

Alzheimer’s•Progressive degeneration of the brain•Lesions (protein deposits) develop in cortex•Short term memory loss is one of the first symptoms

Hydrocephalus

•CSF accumulates in the brain•Skull may become enlarged•May result in brain damage•Monitored during pregnancy

Disorders

Parkinson’s

• Less dopamine released

• Overactive inhibitory movement

• Dopamine can’t pass the blood brain barrier – use L-dopa

BR – Label brain

What are we doing today?

1. Complete brain dissection (may do microscope view if desired)

2. Work on HW

HW –

Ch. 9 #1 – Wed.

Brain dissection – Wed.

Ch. 9 #2 – Th.