“Nerve Impulses”

Membrane potential – + outside, - insideCaused b/c slightly more positive ions (Na+)

outside the membrane than inside (K+)Polarized

All living cells maintain a membrane potential

Positive charges outside membrane attracts negative charges inside membrane.

-70 charge inside membrane

(RMP)- When neuron is not conducting signals.

Normally -70mV because of negatively charged proteins inside neuron which cannot cross the cell membrane

Caused b/c some K+ channels are open at rest so + ions are moving outside the cell creating the positive charge on the outside of the cell.

Gated channels allow for the movement of Na+ and K+ down their concentration gradient at rest.

(Na+ in, K+ out)Sodium-potassium pumps use ATP to move Na+

and K+ against their concentration gradient after an action potential.

1. What causes the membrane of cells to have a membrane potential (a charge)?

2. What is the resting membrane potential inside a cell at rest?

3. Which ions are involved in maintaining RMP?

When a neuron is transmitting an electrical signal along the membrane.

Involves movement of Na+, K+, and Cl- in and out of the cell membrane.

1. When stimulus is enough to reach the threshold potential (-55 mV) voltage-gated Na+ channels open.

2. As Na+ enters the cell it causes a wave of depolarization.

3. Action potential peaks at +30mV and Na+ channels close. K+ channels then open to let K+ out of the cell.

4. After brief hyperpolarization (charge dips below -70mV), resting potential is restored by means of the sodium-potassium pump (Na+ out/K+ in).

Threshold is met.

1. Na+ channels open.

2. Na+ rushes in.

6. Brief hyperpolarization.

7. Sodium-potassium pump balancing out ions.

3. Na+ channels close

4. K+ channels open

5. K+ rushes out.

Action Potential Module

Absolute Refractory period- half a millisecond after stimulation the membrane will not respond to any stimulus.

Relative Refractory period- the membrane will respond only to very strong stimuli.

Refractory period ensures that action potential onlytravels in one direction!!

Some, like benzocaine, block the opening of Na+ channels.

How does this prevent pain transmission???

4. What is an action potential?

5. What is the difference between depolarization and repolarization?

6. During which refractory period can a neuron not be stimulated?

Synapse- the junction where signals are transmitted from the presynaptic neuron to a postsynaptic neuron or to an effector (muscle or gland)

Electrical SynapseAllows for continuous

flow of action potentialFound in cardiac &

smooth muscles

Chemical SynapseUse neurotransmitters

to send signal from pre- to postsynaptic cell.

Found in nervous system

1. Action potential reaches the synaptic knob of the telodendria (structures at the tips of the branches of axon that contain neurotransmitter) and causes Ca++ channels to open.

2. Ca++ rushes into the cell (neuron) triggering the movement of neurotransmitter vesicles to the synaptic knob membrane where they fuse with the membrane.

3. Once released, the neurotransmitters bind to the postsynaptic neuron’s receptors on its dendrites.

4. The opening of ion channels (K+ and Na+) can then cause a postsynaptic potential

Chemical Synapses Action

Excitatory neurotransmitters Cause both Na+ and K+ channels to

open up Na+ in faster than K+ out slower

This creates temporary depolarizationExcitatory postsynaptic potential

(EPSP) Includes Histamine and Acetylcholine in

skeletal muscles.

Inhibitory neurotransmittersCause K+ channels to open up K+ out

This creates temporary hyperpolarization

Inhibitory postsynaptic potential (IPSP)

Includes Serotonin, Dopamine and Acetylcholine in cardiac muscles.

http://www.pbs.org/wnet/closetohome/science/html/animations.html

1. What is a synapse?

2. What is a neurotransmitter?

3. What occurs during an excitatory postsynaptic potential?

4. What occurs during an inhibitory postsynaptic potential?

Neurons stop dividing btwn 6-12 months of age.

Damage to neurons in the brain and spinal cord is permanent.

Damage to neurons in the peripheral nervous system can be repaired if there is no damage to the cell body or neurolemma (outer covering of Schwann cells).

Damaged nerves – regenerate at a rate of 2-5mm per day

Epilepsy2nd most common neurological disorderAbnormal electrical discharges in the brain.

StrokeMost common neurological disorderBlood clot in blood vessel of the brain

“The Central Nervous System”

The Brain and Spinal Cord

CerebrumCerebellumDiencephalonBrain Stem

Cerebral cortex- gray matter on the outside of the cerebrumResponsible for conscious thought,

memory, awareness, language, reasoning.

Limbic system- controls emotions, anger, sorrow and pleasure.

Corpus Callosum-connects the right and left hemispheres

Gyrus (bulge) Sulcus

(crevice)

CerebelluCerebellummControls Controls

skilled muscle skilled muscle movements, movements, posture and posture and balance.balance.

DiencephalonDiencephalon

““between-brain”between-brain” Thalamus Thalamus - detects mild pain - detects mild pain

and temperature sensation, and temperature sensation, determines whether something is determines whether something is pleasantpleasant

Hypothalamus Hypothalamus - connects info - connects info from nervous and endocrine to from nervous and endocrine to maintain homeostasis. Regulates maintain homeostasis. Regulates appetite and feelings of appetite and feelings of satisfaction. Mind-body link.satisfaction. Mind-body link.

Pineal glandPineal gland - - secretes melatonin to secretes melatonin to regulate sleep.regulate sleep.

Medulla OblongataMedulla Oblongata - controls heart - controls heart rate, blood pressure, breathingrate, blood pressure, breathing

PonsPons - helps control vital functions - helps control vital functions MidbrainMidbrain -audio, visual and some -audio, visual and some

muscular control.muscular control.

SkullMeningesCerebrospinal Fluid

Dura Mater (HARD MOTHER) - outer layer, strong white fibrous tissue.

Arachnoid membrane (SPIDER WEB) - middle layer, cobweb-like layer.

Pia Mater (SOFT MOTHER)-inner layer, adheres to the brain, translucent.

Meningitis- inflammation of the meninges caused by bacteria, viral or fungal infections.

Subdural Hematoma- large blood clot found under the dura mater. Usually sign of trauma.

CSF- provides a cushion of protection around brain spinal cord.

Ventricles- 4 fluid-filled spaces in the brain.

Stroke (Cerebrovascular accident CVA) Usually because of a clot; there is a cessation of blood

to the brain and the region is starved of oxygen (ischemia).

Hemiplegia- paralysis on one side of the body.

Huntington disease Involuntary movements, dementia and death

Creutzfeldt-Jakob Human “mad cow” disease. A prion causes protein

denaturization in the brain.

Seizures Sudden burst of neuron activity. Epilepsy is chronic

seizure, normally idiopathic (no known cause).