Nervous System

Ch 9

Pre. And Suf. Quiz Thursday

• Ax- axle gangli- swelling

• Dendr- tree lemm- peel/rind

• Funi-small cord or fiber moto- moving

• Mening- membrane peri-around

• Plex- interweave sens- feeling

• Syn- together ventr- belly/stomach

What is the nervous system?

• A system of nerves and supporting tissues that create the

• Senses (Sight, Hearing, etc..)

• Thought

• Muscle Movement

• Feelings

What is the job of the nervous system?

• Sensory function: Detect changes in and out of the body.

• Motor function: Effect Muscles & glands.

• Integrative function: To connect the Sensory and Motor function. Produces thought.

What are the two major parts of the nervous system and what are

they composed of?• Central nervous system: Brain

and Spinal chord

• Peripheral nervous system: All other nerves

Vs.

Parts of the Peripheral Nervous System (PNS)

• Somatic Nervous System– Called Voluntary Nervous System

• Autonomic Nervous System– Involuntary Nervous System– 2 Major Branches

• Sympathetic– Fight or flight– Liver: glycogen to glucose, Bronchi dilate,

Adrenaline increases, Heart rate and breathing increase

• Parasympathetic– Calms body down. Decreases Heart and

breathing, increases digestion.

Parasympathetic vs. Sympathetic Nervous System

The NSIn Action

Autonomic Nervous System

in Action

What is nervous tissue?

• Neurons: or nerve cells. Conduct the impulses.

• Neuroglial/ Glial cells: nurse cells to neurons. Protect, feed, speed up the signal. May be the cause of Alzheimer's and Parkinson's.– Schwann Cells: form myelin sheath

What are the parts of a nerve?

• Axon

• Dendrite

• Cell Body

• Nucleus

• Myelin

• Node of Ranvier

What are the types of nerve cells?

• Unipolar: used in ganglia. Nucleus is off to the side.

• Bipolar: used in eyes, nose, and ears. Nucleus is in the middle.

• Multipolar: used in brain and spinal cord. Nucleus is within the dendrites.

Nerve Cell

• Cell body: cytoplasm, organelles: mitochondria, lysosomes, golgi apparatus, and Nucleus.

• Dendrites: pick up the nerve signal.

• Axon: Long, may be branched carry nerve signals Away.

Review of

A Neuron

Do nerve cells reproduce once mature?

• No. That is the problem. They can grow axon ends, but once the nucleus is damaged that nerve will not grow back.

What are Neuroglial Cells?

• Schwann cells: wrap around axon and speeds up nerve signals. Mainly fat called Myelin. Can’t carry nerve signal so the charge jumps over them at the nodes of Ranvier. = Grey Matter

• Astrocytes: Structural support & feed• Microglial Cells: Phagocytize

invaders & broken cell parts

What difference does it make if a nerve has Schwann cells or not?

• Nerves that have a large diameter and are myelinated are super-fast: 120m/s

• Nerves with a small diameter that are unmyelinated are slow: 0.5m/s

How do nerves communicate?

• Through Neurotransmitters: chemical signals sent from the Axon terminals of the nerve.

• Nerves communicate through electrical signals.

• These electrical signals are created through action and resting potentials.

How is an action potential reached?

• Change in nerve membrane permeability. Na+ rushes in the nerve is depolarized (loses its charge).

• K+ then rushes out which repolarizes the nerve cell.

• 1/1000 of a second. Both steps together are the action potential.

• Active transport soon reestablishes the resting potential.

Action Potential

Action Potential Explained

So… How does a nerve signal reach resting potential?

• Nerve has a slightly negative charge inside and a slightly positive charge outside at rest. = Polarized See fig 7.9

• K+ ions are inside, Na+ ions outside. Negative charge can’t diffuse through the membrane.

• Active transport is used to push Na+ out and K+ in. More + leave than enter= neg. charge inside.

What do muscles and nerves have in common?

• All or none response. The nerve impulse is either conducted or not. The intensity of the signal does not change.

How is an action potential sent?

• Write one paragraph explaining it without looking in your notes.

• Someone or someone's will be chosen to read their explanations to the class.

How are Neurotransmitters released?

• Action potential causes Ca+ ions to enter the terminal end of the axon.

• Synaptic vesicles then fuse with the membrane.

• Contents are released into the synaptic cleft.

• Neurotransmitters are decomposed and the vesicles retreat to be refilled.

How do Neurotransmitters Communicate?

Neurotransmitter Actions NIH Worksheet

Group Work: Summarize how you think the neuron works.

NIHNeurotransmitters

What is a Synapse?

• The junction between two communicating nerves.

• Presynaptic neuron to the synaptic cleft to the Postsynaptic neuron

Synaptic Cleft

Impulse

Presynaptic neuron

Vesicle

Transmitters

Synaptic cleft

Receptors

Postsynapticneuron

Postsynaptic activity

If a drug like procaine decreased the membrane permeability to Na+

ions, what would be the effect?

• Impulses from one nerve can not pass to the next region. The action potential can’t be reached. Used by doctors as a local anesthetic.

What kind of neurotransmitters cross the synaptic cleft?

• Acetylcholine: Muscles

• Epinephrine/ Adrenaline: Fight or Flight

• Norepinephrine: almost the same as epinephrine but has no effect on the heart.

• Dopamine: brain functions: not working= schizophrenia and Parkinson's

• Seratonin: suppresses pain impulses

Need a review? Hit the button.Go through each of them EXCEPT the second one.

How does a reflex work?

• Reflex Arc

• Stimulus Receptor end of a Sensory neuron Interneuron (reflex center, often the spinal cord) Motor neuron Effector (Muscle being moved)Response

Reflex Arc

Can you control a reflex?

• No. Reflexes are automatic & unconscious.

• Anesthesiologists will often use this information to test if the medicine is working.

Reflex

Lab

Some neurons are Sensory Receptors

• Naked Nerve Endings=Pain

• Meissner’s Corpuscles= Touch

• Pacinian Corpuscles= Deep Touch

• Many Others: Figure 7.7

Factoid: Your funny bone is really yourUlnar nerve (close to the surface of your body.)

What do other neurons do?

• Mirror Neurons in the Brain

PBS Special: 2005 14 minutes

On Mirror Neurons