The Nervous System
Evelin Morales Period 5

Action Potential

Neurotransmitters

2 or 3 different neurotransmitters

bind to specific receptor molecules, opening ion channels and thereby stimulating impulse conduction by the membrane

Definition- chemical compounds release from axon terminals (of a presynaptic neuron) into a synaptic cleft

  1. strong enough stimulation/ stimulus causes Na+ gates to open

Na+ rush into cell causing depolarization

-70mV + 30 mV

nerve impulse is transmitted during action potential

2.if a strong enough depolarization occurs, threshold potential is reached and impulse is sent down axon

  1. K+ rush out of neuron after Na+ rushes in, depolarizes membrane
  1. membrane is hyper polarized- too many K+ leave the cell. Membrane potential dips below resting potential.

Final Step= resting membrane potential is restored

some degraded by enzymes

some reuptake into cells

Spinal Cord Structure

Inner portion is an H- shaped core comprised of gray matter= dendrites and cell bodies of neurons

Outerr portion is formed by columns of white matter, which is made up of spinal tracts= bundles of myelinated nerve fibers

occipital bone to the first lunar vertebra

Ascending tracts: sends impulse up towards the brain

Descending tracts: sends impulses down the cord from the brain

Spinal cord Functions

2.

1).

contains centers for thousands of reflex arcs in the spinal cord

Spinal cord reflex: reflex that result from

Interneuron: transfers sensory impulses to outgoing motor impulses

  1. Jerk reflex
  1. Withdrawal reflex

if any injury cuts across the entire spinal cord, impulses cannot travel anywhere below the injury, which leads to...

Paralysis: loss of ability to make voluntary movements

Anesthesia: loss of sensation

Coverings of Brain and Spinal Cord

  1. Dura mater: tough, outer layer lining the vertebral canal
  1. Pia mater: innermost membrane surrounding the actual cord
  1. Arachnoid matter: membrane in between the dura mater and the Pia mater (like a cobweb; remember, "arachne" means spider)

Main Divisions of the Nervous System:

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

Two Division of PNS:

  1. Sensory (afferent) Nerves

they are affected by the environment or sense the environment

Interneuron- nerves that connect sensory nerves to motor nerves

relay information from skin, muscles, and glands to CNS

  1. Motor (efferent) Nerves

they cause an effect or response

carry impulses from CNS to organs muscles

2 types- Somatic nervous system and Autonomic nervous system (ANS)

Motor Neurons:

2 types of motor neurons

1.Somatic motor neurons

conscious voluntary control

sense and respond to external environment

  1. Autonomis motor neurons

respond to interna environment

automatic, unconscious, involuntary control

Structure of a Neuron

Dendrite- receives impulse and sends signal to the cell body

Cell body- metabolic center

Axon- conducts signal away from the cell body

Myelin- fatty substance that insulates signal , and allows signal to be sent faster

Node(s) of Ranvier- spaces between myelin/ Schwann cells

3 types of Neuron structure:

  1. multipolar- many dendrites, one axon
  1. bipolar- one dendrite, one axon (sensory)
  1. unipolar- fused axon and dendrite (sensory)

Nerve Coverings:

= made up of fibrous connective tissue

Fascicle= a group of nerve fibers (group of wrapped axons)

Endoneurium- surrounds individual fibers within a nerve

Perineurium- surrounds a group of nerve fibers

Epineurium- surrounds the entire nerve

Reflex Arc.

= pathway of a reflex response

5 parts of reflex arc:

  1. sends signal to CNS
  1. connection
  1. delivers response
  1. sensory receptor- nerve ending detects stimulus
  1. target organ responds

Name of all the lobes and their function

  1. Frontal Lobe
  1. Temporal
  1. Occipital Lobe
  1. Parietal Lobe

processes vision (visual cortex)

size, shape, color, pain, temperature and speech

Post- central Gyrus= Somatic Sensory Area- interprets sensory info

hearing, speech, memory, sequencing and organization

personality/ emotions/ intelligence

Precentral gyrus= Primary Motor Cortex

logic/ problem solving

attention/ concentration

controls conscious movement of skeletal muscle

Broca's area- ability to vocalize words (usually L hemisphere)

Compare and contrast the autonomic system

the ANS can be subdivided into the parasympathetic nervous system (PSNS) and the sympathetic nervous sytem (SNS)

the somatic nervous system (SoNS) is the part of the peripheral system

associated with the voluntary control of body movements throughout the skeletal muscles and mediation of involuntary reflex arcs

Subdivisions of the nervous system

the nervous system is comprised of two major subdivisions, the central nervous system (CNS) and the peripheral system(PNS)

Major part of the brain (4 Major Regions)

1.Cerebrum (Cerebral Hemispheres)

  1. Brain Stem
  1. Cerebellum
  1. Diencephalon

has gray matter, white matter and basal nuclei

largest mass of the brain (83%)

superior part of the brain composed of two hemispheres( "higher brain")

allows us to remember the past, plan for the future, and imagine tings that have not happened

responsible for voluntary or conscious activities

Gyrus (gyro)= bump, elevated ridges of tissues

Fissures= deeper grooves, usually separate large parts of the brain

the longitudinal fissure divides the cerebrum into Land R hemispheres (L hemisphere controls r side of body)

sulcus(sulci)= creases, shallow grooves

contains 2 main parts:

sits on top of the brain stem

  1. Thalamus
  1. Hypothalamus

relays sensory info., recognizes good vs. bad sensation

controls body temp, water balance, metabolism and endocrine function...

a part of the limbic system (thirst, appetite, sex, pain, and pleasure)= "lower brain"

B. Pons: relay between cerebrum and cerebellum

C. Medulla oblongata: reflex center for heart rate, B.P. treating, vomiting, and swallowing

A. Midbrain: reflex center for vision and hearing

Reticular Formation controls wale/ sleep cycle

10% of brain volume but over 50% of the total number of neurons in the brain

damage causes ataxia= clumsy movements and loss of balance

muscles of body to move smoothly

equilibrium and balance (and posture)

The layers of the meninges

Meninges= three layers of tissue that cover and protect the brain

membranes located between bone and soft tissues of nervous system

Outer= Dura Matter (tough mother)

Inner= Pia Mater (gentle mother) covers every fold of brain

Middle= Arachnoid mater (looks like cobweb)

Spaces and Ventricles

Cerebrospinal Fluid (CSF)

Blood-Brain Barrier protects from toxins in blood

C.S.F. (Cerebrospinal Fluid)- watery "cushioning" that the brain floats in

protects, cushions, nourish brain and spinal cord

ependymal cells from a blood- cerebrospinal fluid barrier

formed by choroid plexuses

protecting brain from harmful substances (and therapeutic drugs)

Spinal Tap

removing CSF from the lumbar region of the spinal cord

used for diagnosis or treatment

Function of neuron

are electrically excitable cells in the nervous system that function to process and transmit information

neurons also known as neurons, nerve cells and nerve fibers

in vertebrate animals, neurons are the core components of the brain, spinal cord and peripheral nerves.

Classification of neurons

sensory neurons (afferent neurons) are unipolar, bipolar, or multipolar shaped cells

these cells conduct action potentials toward or into the central nervous system

nerve cells are functionally classified as sensory neurons, motor neurons, or interneurons

Diseases associated with the brain

Concussion- shaking of the brain, no permanent damage, mostly result of swelling; loss of consciousness; dizziness; headache

Contusion causes tissue destruction, permanent damage

Intracranial hemorrhage- bleeding in the skull, edema; (skin Baby Syndrome)

Dementia

"Forgetfulness"

destruction of neurons

degenerative and irreversible

loss of brain function

affects memory, language, attention span, intellect, personality, cognitive skills

most common type is Alzheimer's

Parkinson's disease, multiple sclerosis, or Huntington diseases are a few other that can lead to dementia

CVA (Cerebrovascular Accident) - aka stroke- blood flow to brain tissue is blocked causing cell death.

Drugs that affect the brain

A combination of opiates (heroin or prescription painkillers) and alcohol can be especially dangerous.

In the United States, prescription opiates are the cause for kore deaths by overdose than any other single drug.

Most people who overdose are under the influence of more than one drug.

Most of these deaths ultimately result from respiratory failure.

Poly drug Cocktails: Opiates and Alcohol

Alcohol overdose occur mainly in two ways.

FIRST, by decreasing the excitatory effect of glutamate, alcohol causes unconsciousness.

At high levels, it can also slow or stop breathing.

Second the body tries to get rid itself of unabsorbed alcohol by emptying the stomach.

Nicotine

It is possible to overdose on nicotine by using combinations of nicotine patches or nicotine gum and cigarettes at the same time.

sometimes, nicotine can reach levels high enough to paralyze the muscles that control breathing or cause a heart break.

Smoking cigarettes can kill by causing lung cancer, but it cannot lead to a nicotine overdose.

Cocaine and Other Stimulants