Endocrine System

Nervous System EndocrineSystem

Both

Fast Action

Short-term Effects

Only target cells get signal & respond

Neurons

Slow Action

Long-term Effects

All cells get signal-only target cellsrespond

Glands & Hormones

Monitor Stimuli

Process Info

Respond to Stimuli

Maintain Homeostasis

Functions include:

Sensation Integration center Reaction (Response)

A network of billions of nerve cells linked together in a highly organized manner to act as the control center of the body.

Sensation:

Monitors stimuli (inside and outside the body)

Integration:

Processes and Interprets sensory information

Response/Reaction:

Activates muscles or glands

Central nervous system (CNS) Brain & Spinal Cord

Peripheral nervous system (PNS) Cranial nerves-

neck & head

Spinal nerves- spinal cord to lower extremities

Somatic nervous system VOLUNTARY (generally) Conduct impulses from the

CNS to skeletal muscles

Autonomic nervous system INVOLUNTARY Conducts impulses from

the CNS to smooth muscle, cardiac muscle, and glands.

Sympathetic NS“Fight or Flight”

Parasympathetic NS“Rest and Digest”

These two systems are antagonistic.

Typically, we balance them to keep ourselves in a state of dynamic equilibrium.

Two cell types:

1. Neuroglia (“glial cells”)Supporting cells90% of CNS

2. NeuronsFunctional, signal-conducting cells

OVERVIEW

Glial cells

Neuron

Example: Schwann cells

• Form myelin sheaths around the larger nerve fibers in the PNS.

• Vital to neuronal regeneration

Neuroglia

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dendrites

cell body

axon

synapse

Neuron = a nerve cell

signal direction

signaldirection

The most specialized cells in animals The longest cells:

Blue Whale neuron = 10-30 meters Giraffe neuron = 5 meters Human neuron = 1-2 meters

Nervous system allows for 1 millisecond response timeNervous system allows for 1 millisecond response time

Neurons are:

Dendrite

Axon

terminals

Cell body

AxonMyelin sheath

Node of Ranvier(Myelin Sheath Gap)

Myelination in the CNS

Myelination in the PNS

A Schwann cell is glial

2003-2004

signaldirection

myelin coating

Multiple Sclerosisimmune system (T cells) attacks myelin coating loss of signal

Multiple Sclerosisimmune system (T cells) attacks myelin coating loss of signal

Axon coated with insulation made of myelin cells

= speeds signal signal hops from node to node

330 mph vs. 11 mph

Resting potential Neuron at rest: - inside of the neuron is negative relative to the outside. - concentrations of ions attempt to balance out on both

sides of the membrane - ions cannot balance because the cell membrane allows

only some ions to pass through ion channels.

There is a charge imbalance. (The resting membrane potential of a neuron is about

-70 mV).

At rest, there are more sodium ions outside the neuron and more potassium ions inside the neuron.

Stimulus causes potential difference to move toward 0 mV.

When potential difference reaches -55 mV (threshold level), neuron will fire an action potential.

When threshold level is reached, an action potential of a fixed sized will always fire. "ALL OR NONE".

1

2

Na+ transport proteins

They have 2 gates

3

4 5

Between the opening of the Na+ channel activation gate

and the opening of the inactivation gate, a Na+ channel CANNOT be stimulated.

This is the REFRACTORY PERIOD. Action potential is unidirectional.

All or none response   

Threshold stimulus   

Refractory period  

Clogs

- Toilet handle triggers flushing. Voltage-gated channels trigger an action potential if the membrane is stimulated with enough voltage.

- If pressed hard enough, a complete flush will occur. Pushing harder on the handle will not make a bigger flush. This is true for the action potential: all-or-none.

- Flush involves movement of "materials" through plumbing.The action potential involves movement of Na+ and K+ ions through voltage-gated channels.

- The force for fluid movement in the toilet is water pressure. The ‘pressure’ for ion movement is an electrochemical gradient.

- Toilets can clog so materials cannot move.Drugs and toxins can prevent ion movement and “clog” the action potential.

Unmyelinated neurons undergo continuous chemical conduction

Myelinated neurons undergo saltatory conduction - alternating electrical conduction and chemical conduction.

In this situation, the wave of depolarization travels along the axon

Analogous to dominos falling

In unmyelinated axons:

Saltare is a Latin word meaning “to leap.”

The Myelin Sheath is segmented. There are ‘myelin-free’ regions along the axon, called the nodes of Ranvier, or Myelin Sheath Gaps.

Myelinated axons: Saltatory Conduction

1. Which do you think has a faster rate of AP conduction – myelinated or unmyelinated axons?

2. Which do you think would conduct an AP faster – an axon with a large diameter or an axon with a small diameter?

The answer to #1 is a myelinated axon. Could you move 100m faster if you walked heel to toe or if you bounded in a way that there were 3m in

between your feet with each step?

What about throwing an object?

The answer to #2 is an axon with a large diameter. Could you move faster if you walked through a hallway that was 4 m wide or if you walked

through a hallway that was 1m wide?

Synapses

Junction between nerve cells 1st cell releases chemical to

trigger next cell Where drugs may affect N.S.

2003-2004

animation

1. Electrical current travels down the axon

2. Vesicles with chemicals move toward the membrane and merges with the membrane of synaptic bulb

3. Chemicals are released and diffuse toward the next cell’s plasma membrane

4. The chemicals open up the transport proteins and allow the signal to pass to the next cell

http://learn.genetics.utah.edu/content/addiction/reward/neurontalk.html

Cerebrum

Corpus callosum

Cerebellum

Thalamus

Hypothalamus

Midbrain

Pons

Medulla oblongata

Spinal cord

Functions Basic body functions:

breathing, heart, digestion, swallowing, vomiting Homeostasis Coordination of movement

The “lower brain” medulla oblongata pons cerebellum

Cerebrum2 hemispheres left controls right side of body; right controls left

Corpus callosumThe connection between the 2 hemispheres

Left hemisphere “Logic side” Language, math, logic, vision & hearing Fine motor control

Right hemisphere “Creative side” Pattern recognition, spatial

relationships, non-verbal ideas, emotions, multi-tasking

Regions specialized for different functions Lobes

Frontal: speech, control of emotions Temporal: smell, hearing Occipital: vision Parietal: speech, taste, reading

frontal

temporal occipital

parietal

Controls basic emotions (fear, anger), involved in emotional bonding, establishes emotional memory

Occipital lobe- visual processing

Temporal lobe-memory, sound processing, auditory stimuli

Frontal lobe- higher thought functions, judgment, personality, emotion, problem-solving, planning, movement

Parietal lobe- sensation, language (left side)

Pons- breathing, relay

Organs of the Peripheral Nervous System (PNS)

1.Nerves=a true organ (made of different tissue) and performs one functionFunction: transport nerve impulses from one part of the body to another

2. Ganglia = clusters of neuron cell bodies located outside the CNS

Reflex, or automatic response

Rapid response: automated

Signal only goes to spinal cordNo higher level processing=Does not involve brain

AdvantageDon’t need to think or make decisions about: Ex’s: Blinking, balance, pupil dilation, flinching

Accidents Drugs Alcohol Disease

Contagious Hereditary

http://learn.genetics.utah.edu/content/addiction/drugs/mouse.html

What if neurons die or get damaged

here?

or hereor here

or here

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Function: Chemical regulation of bodily processes-Uses hormones

-Called ductless glands (secrete directly into bloodstream)

Chemical messengers Secreted from glands/cells- in small

amounts Travel through bloodstream Act on Target cells (receptors)

▪ Effect rates of reactions/processes▪ Enzymes rates▪ Protein synthesis▪ Transport of materials across a membrane

Negative Feedback:-Response in opposite direction of stimulus-Like a thermostat-Ex. Parathyroid hormone- Regulates Calcium levels

Ca2+ rise= stops secretion of hormone

Positive Feedback:-Response in same direction as stimulus-When positive response, signals release of moreEx. Oxytocin= Uterine contractions during childbirth

-Increase strength of contraction until birth

video

GLANDPituitary(GH, PRL, TSH, ACTH, MSH, FSH, LH)

Thyroid(T4, T3, Calcitonin)

Parathyroid(PTH)

Pineal (Melatonin)

Thymus (Thymosin)

FUNCTION Growth, Skin, Breast milk,

Metabolism, Ova, Sperm, Gonads, Fluid balance

Metabolism, Growth, Ca2+ levels

Ca2+ / Phosphate levels

Inhibit secretion of FSH and LH, animal sleep-wake cycles, other cycles

Stimulates maturation of T lymphocytes

Adrenal(Epinephrine, Norepinephrine)

Pancreas (Glucagon, Insulin)

Gonads Ovaries (Estrogen)

Testes (Testosterone)

“Flight or Fight” Response- metabolism, HR, BP

Conversion of glycogen to glucose (Glucagon) and conversion of glucose to glycogen (Insulin)

Sexual development

Estrogen: female sex characteristics, ovarian cycle, and menstrual cycle

Testosterone: male sex characteristics and sperm cell production