9 - The Biology Corner



9.7 The Synapse

Synapse – junction between two communicating neurons

Nerve pathway – nerve impulse travels from neuron to neuron

Synaptic Transmission

Dendrite ( cell body ( along axon ( synapse (gap)

To complete the signal, a NEUROTRANSMITTER is released at the gap to signal the next neuron

Excitatory – increase membrane permeability, increases chance for threshold to be achieved

Inhibitory – decrease membrane permeability, decrease chance for threshold to be achieved

Types of Neurotransmitters

Acetylcholine – stimulates muscle contraction

Monoamines – Norepinephrine & Dopamine (sense of feeling good, low levels = depression)

Serotonin (sleepiness)

Endorphins (reduce pain, inhibit receptors)

Synapses are highly susceptible to drugs and fatigue

• Curare (poison used by S. American Indians) and atropine stops Acetylcholine from depolarising the post-synaptic membrane, i.e. become paralysed.

• Strychnine and some nerve gases inhibit or destroy acetylcholinesterase formation. Prolongs and enhances any stimulus, i.e. leads to convulsions, contraction of muscles upon the slightest stimulus.

• Cocaine, morphine, alcohol, ether and chloroform anaesthetise nerve fibers. (inhibitory)

• Mescaline and LSD produce their hallucinatory effect by interfering with nor-adrenaline & serotonin

9.8 Impulse Processing

Neuronal pool – groups of neurons that make hundreds of synaptic connections and work together to perform a common function

9.9 Types of Nerves

Sensory Nerves – conduct impulses into the brain or spinal cord

Motor Nerves – carry impulses to muscles of glands

Mixed Nerves - contain both sensory and motor nerves

9.10 Nerve Pathways

Reflex arc – simple pathway, includes only a few neurons (reflexes)

Reflex Behavior – automatic, subconscious responses to stimulu

Knee-jerk reflex (patellar tendon reflex)

stimulus knee ( sensory nerve ( spinal cord ( motor nerve

Withdrawal reflex – occurs when you touch something painful

9.11 Meninges = membranes located between bone and soft tissues of the nervous system

Dura mater = outmost layer, blood vessels, nerves

Arachnoid mater = no blood vessels, located between

Pia mater = contains many nerves and blood vessels to nourish cells of brain and spinal cord

*Cerebrospinal fluid = between arachnoid and pia maters

9.12 Spinal Cord - nerve column, passes from brain down through the vertebral canal

- has 31 segments, each with a pair of spinal nerves

Cervical enlargement = supplies nerves to upper limbs (neck)

Lumbar enlargement = supplies nerves to the lower limbs (lower back)

FUNCTION: conducting nerve impulses, serves as a center for spinal reflexes

Ascending tracts = carry sensory info to the brain

Descending tracts = carry motor impulses from the brain to the muscles

Spinal reflexes – reflex arcs pass through the spinal cord

9.13 Brain

Three Major Parts:

Cerebrum – largest, sensory and motor functions, higher mental function (memory, reasoning)

Cerebellum – coordinate voluntary muscles

Brain stem – regulate visceral functions

DESCRIBE THE FUNCTIONS:

1. Cerebral Hemispheres

2. Corpus Callosum

3. Convolutions / Sulcus / Gyrus

4. Transverse / Lateral / Longitudinal Fissures

Lobes of the Brain

5. Frontal Lobe

6. Parietal Lobe

7. Temporal Lobe

8. Occipital Lobe

9. Cerebral Cortex

10. Ventricles

11. Cerebrospinal Fluid

Functional Regions:

12. Motor

13. Sensory

14. Association

DIENCEPHALON & BRAIN STEM

1. Diencephalon

2. Thalamus

3. Hypothalamus

4. Optic Tract / Chiasma

5. Midbrain

6. Pons

7. Medulla

8. Pituitary Gland

9. Hippocampus

10. Limbic System

TYPES OF MEMORY: Episodic | Procedural | Semantic | Working

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