neuron

NEURAL SIGNALLING

• Neuron: Specialized nerve cen that is the functional unit
  Of the nervous system

• Allows organism to receive and respond to internal and external stimuli.

• Neural signalling: communication via neurons

1. Reception: detection of Stimulus

• Neurons and specialized sensory receptors (eyes and skin)

2. Transmission: movement of message diong neuron to another neuron or muscie or gland

3. Integration: sorting and interpreting of messages and determination of response

   4. Response: output or action resulting from integration or neural messages

Functional Classes of Neurons

Information-Processing Steps in Nervous System:

1. Stimulus reception by sensory receptors on afferent neurons

2. Message transmission to interneurons (brain/spinal cord)

making sense of the info

3. Integration of messages in interneurons (brain)

given by afferent neurons

4. Response → transmission of neural messages by efferent neurons to effectors (muscle/gland

nerves

• Many axons are bundled together to form nerve fibres → aka
  nerves.

• Branch extensively throughout the periphery of the entire body.

NEURON SUPPORT SYSTEM

• Electrical signals are produced in cell body of neuron.

• Ions flowing down concentration gradients through channels in plasma membrane.

• Glial cells: provide nutrition and support to neurons untena o Retain capacity to divide → source of nearly all brain tumours.

• Schwann cells: form tightly wrapped lavers of piasma memorane

• Myelin sheaths: the insulated covering formed loy schwann

• Recall: High lipid content

• Nodes of Ranvier: gaps between schwann cells

• Expose axon membrane to extracellular fluid

• Allows for rapid conduction of nerve impulses

Neuronal Circuit

• Connections between the terminals of one neuron and the dendrites or cell body of a second neuron.

one or mores

Afferent neuron → 1* interneurons → efferent neuron

• Interneurons may receive information from several afferent neurons

• Interneurons may connect to several efferent neurons

REFLEX ARC

Neural Circuit: the coordination of the receptor, afferent neuron, interneuron, efferent neuron, and effertor in response to

stimulis

Reflex Arc: a neurai circuit that tratis through the Spinal cord lout does not require the coordination of the brain

→ allows for reflex actions

Synapse: connections between neurons

or between neurons and effectors

купорііс

wice

Chemical Synapse: a synapse in which a

neurotrans

neurotransmitter moves from a presunaptic cel to a postsynaptio

Neurotransmitter (NT): Cel through the synaptic cleft a chemical that is released from vesicles into synapois to facilitate nerve signal transmission

Synaptic Cleft (often referred to as synapse): the tiny gap between presynaptic ana post synaptic cels in a chemical

synapse, across which the neurotransmitter diffuses

Electrical Synapse:

a synapse in unich the presynaptic cel makes direct contact with the post synaptic cell, anowing current to flow via a gap junction between cells.

Conduction of Electrical Signals

postrynopic dendie

Recall: the separation of +ve and -ve charges across the plasma membrane → outside +ve, inside -ve → creates voltage/electrical potential difference.

Membrane Potential: the electrical potential of a membrane, Which is caused by an imbaiance of charges on either side of the membrane.

Excitable Cells: cells that respond to stimuli causing their memorane potential to change rapidly.

• Stimuli = electrical, chemical, mechanical

• Muscle and nerve cells

• Produced by sudden flow of ions across plasma membrane → nerve impulse.

Resting Membrane Potential

• Na+ /K* active transport pump

• net positive charge outside the cen

• inside there are many anions a5 well to add to -ve charge

• Resting potential: the voltage difference across a nerve cel memorane of an unstimulated neuron ;
  typically, - 70 mv

• RP other than 0 → polarized

• Action Potential: the voltage difference across a nerve cel memorane
  When the nerve is excited

• begins when stimuius causes + ve charges from outside neuron to flow inward