Fundamentals of Biology: Lecture Outlines: Chapter 34 Integration and Control

3 Classes of Neurons:

1. Sensory neuron

2. Interneuron

3. Motor neuron

 

Functional Zones

INPUT ZONE

 

 

TRIGGER ZONE

 

 

CONDUCTING ZONE

 

 

OUTPUT ZONE

 

 

How do ions move?

- Passive or Active Transport

Resting Membrane Potential

- inside neuron is slightly negative

Due to:

1. Concentration of ions

 

2. Membrane permeability

- relates to channel proteins

The membrane is:

 

 

3. Active transport

- sodium-potassium pump

- driven by ATP

 

 

Graded / Local Signals

- ions flow across membrane in response to stimulus

Graded = vary in magnitude

 

Local = do not spread

 

Depolarization

- inside cell becomes less negative

 

Hyperpolarization

- inside cell becomes more negative

 

Threshold

- if stimulus is intense or long lasting

- graded signals spread to TRIGGER ZONE

 

Positive Feedback

- threshold stimulus causes sodium to flow into neuron

 

 

All-or-Nothing Spike

1. Graded depolarization

 

2. Reaches threshold

- sodium channels open

- sodium ions flood into cell

 

3. Repolarization begins

- sodium channels close

- potassium channels open

 

4. Sodium channels return to normal

- potassium channels close

- at end of refractory period

 

Chemical Synapses:

- at junction between neuron and a cell

- release chemical (neurotransmitter)

 

Presynaptic cell:

- action potential arrives

- gated protein channels

- allow calcium ions in

- calcium causes

- release neurotransmitter

 

Postsynaptic cell:

- protein receptors bind

- changes shape

- opens

- can be excitatory or inhibitory

 

Neurotransmitters:

GABA

Acetylcholine (ACh)

 

Neuromodulators:

Substance P

Endorphins

 

Synaptic Integration

- excitatory and inhibitory signals compete

 

EPSP

- excitatory postsynaptic potential

 

IPSP

- inhibitory postsynaptic potential

 

What happens to the neurotransmitters?

1. Diffuse

2. Removed from synaptic cleft

3. Pumped back inside

 

 

Anatomy of Nerves:

- Nerve = many sensory and/or motor neurons

- between brain or spinal cord and

 

Covered by 3 layers of connective tissue

 

Myelin Sheath

- cover axons

- series of Schwann cells

- exposed nodes

- action potentials jump

 

Clinical example - Multiple sclerosis

Reflex Arc

Reflexes =

 

Muscle Spindles

 

1. Stimulus

2. Muscle spindle stretches

3. Stimulates sensory neurons

4. Action potentials generated

5. Sensory neuron synapses with

6. Action potentials along

7. Neurotransmitter released

8. Response

- contraction of skeletal muscle

 

Botulism

- caused by bacterium

Effect?

Symptoms?

 

Tetanus

- caused by another bacterium

Effect?

Symptoms

 

Vertebrate Nervous Systems

Functional Divisions

CNS

PNS

Somatic

Visceral

 

Tracts

White matter

Gray matter

 

PERIPHERAL NERVOUS SYSTEM

12 pairs

31 pairs

8

12

5

5

1

 

Cranial and Spinal nerves

Somatic Sensory Division

General

Special

Visceral Sensory

General

Special

Somatic Motor Division

Visceral Motor Division

 

CENTRAL NERVOUS SYSTEM

Spinal Cord

Brain

Hindbrain

Medulla oblongata

Cerebellum

Pons

Midbrain

 

Forebrain

Cerebrum

Thalamus

Hypothalamus

 

Brain Cavities and Canals

CSF =

 

- found in 4 ventricles

 

Blood-Brain Barrier

- protects

- controls

- allows passage of

- does not allow

 

HUMAN CEREBRUM

 

Left hemisphere

Right hemisphere

 

Corpus Callosum

Cerebral Cortex

 

Lobes of the Cortex

Occipital

Temporal

Frontal

- primary motor cortex

- body spatially mapped

- many neurons

- fewer for

- stroke

Parietal

- primary somatosensory cortex

 

 

Review:

Review Questions 1-8, 10, 11

Self Quiz 1-7

Critical Thinking #4