Central Nervous System

Front 1

The nervous system

Back 1

A communication network that enables an individual to respond or adjust to changes in internal and/or external environment

Front 2

Components of Nervous System

Back 2

Sensory- detect changes

Integrative- process the sensory data coupled with the stored memory

Motor- provides response to the processed information

Front 3

Neuron Cell

Back 3

A Cell Body: Containing a nucleus, ER, mitochondria and other typical organelles
The Dendrites: Bringing information to the cell body. They are like small branches, allowing to connect to more than one other
neuron. They are what allow the neuron to talk to other cells or perceive the environment.
The Axon: Nerve Fibre, is the longest fibre of the neuron which brings information away from the cell body to the connecting neuron.

Front 4

Types of Neurons

Back 4

Front 5

Somatic sensations

Back 5

Sensation from the skin, muscles, bones, tendons and joints

Activation of a number of distinct somatic receptors

Detect changes in heat, cold, touch, pressure, limb position, limb movement, or pain

Front 6

Somatic sensations Diagram

Back 6

Front 7

Somatic receptors tracts

Back 7

The Anterolateral Tract
Pathways cross over to opposite side of spinal cord to ascend.
e.g. from pain or temperature receptors.
The Dorsal Tract
Pathways ascend ipsilateral (same side of body) and then cross over in brainstem.
e.g. from vibration or joint position receptor.

Front 8

Somatic receptors tracts Diagram

Back 8

Front 9

Somatic receptors destiation

Back 9

Somatic receptors on left side of body go to the right cerebral hemisphere and vice-versa, both for anterolateral and dorsal tracts.

Front 10

Somatosensory cortex

Back 10

Front 11

Receptor types

Back 11

Front 12

Pacinian corpuscles

Back 12

- Found deep in the dermal layers of both hairy and glabrous skin

- Have relatively large endings that are widely spaced.
- Relatively large receptive field per cell.
- Rapidly evoke action potentials
- Adapt and stop firing throughout the stimulus, and then fire action potentials at the end of the stimulus.
- This rapid adaptation allows rate and pressure detection of the stimulus.

Front 13

Ruffini’s endings

Back 13

Found deep in the dermal layers of both hairy and glabrous skin.
Have relatively large endings that are widely spaced.
Relatively large receptive field per cell. Continue to respond during stimulation, i.e. Slowly adapting.

Front 14

Meissner’s corpuscles

Back 14

approx. 1/10 the size of Pacinian corpuscles.

- Located in ridges of glabrous skin, e.g. raised parts of fingerprints.
- Small receptive field compared with Pacinian and Ruffini.
- Rapidly adapting.

Front 15

Merkel’s disk

Back 15

located in the epidermis. Consist of a nerve terminal and a flattened non-neural epithelial cell. Small receptive field.
Slowly adapting.

Front 16

Hair follicle receptors

Back 16

hairy skin only. Can be either rapidly
adapting or slowly adapting.

Front 17

Pain sensation

Back 17

Receptors, “nociceptors”
Respond to stimuli that is about to cause tissue damage, (such as excessive mechanical strain, excessive heat, and chemicals released
from nearby cells and damaged tissue, such as neurotransmitters)

Front 18

Four classes of nociceptors

Back 18

Mechanoreceptors, thermal receptors, chemoreceptors, and polymodal receptors (these respond to all 3 stimuli).

- Nociceptors are similar to other receptor types but generally respond to higher levels of stimulus.

Front 19

Pain stimulus, sensation and suppression

Back 19

Front 20

Neuron Communication

Back 20

An electrical impulse travels down an

axon and to the synaptic terminal Synapse
A synapse consists of 3 parts:
A presynaptic ending: containing
neurotransmitters.
A postsynaptic ending: containing
receptor sites for the neurotransmitters
A synaptic cleft: or space between the
presynaptic and post synaptic endings.

Front 21

Neuron Communication Diagram

Back 21

Front 22

Events in Neuromuscular Transmission

Back 22

1. Depolarization of motor neuron and generation of action potential
2. Action potential travels down the nerve fiber to the neuromuscular junction
3. Depolarization of the axon terminal causes an influx of Ca2+
4. Influx of Ca2+ triggers fusion of the synaptic vesicles of the cell membrane and release of neurotransmitter (Acetylcholine; ACh)
5. Acetylcholine diffuses across the synaptic cleft and binds to post-synaptic ACh receptor (AChR) located on the muscle fiber at the motor end-plate
6. Binding of ACh to AChRs opens the channels causing an influx of Na+
7. Depolarization of the sarcolemma that travels down the t-tubules
8. Release of Ca2+ from the sarcoplasmic reticulum – muscular contraction
9. Unbound ACh in synaptic cleft defuses away or is hydrolyzed (inactivated) by acetylcholinesterase (AChE)

Front 23

Neuromuscular Transmission Diagram

Back 23