Nervous System Vertebrate Nervous Systems Two major subsystems

Nervous System

Vertebrate Nervous Systems Two major subsystems: 1. central nervous system (CNS) – brain and spinal cord 2. peripheral nervous system (PNS) – nerves outside of the brain and spinal cord

Brain

Spinal Cord Miami Project – Spinal Cord Injury Research

Peripheral Nervous System Contains two main nerve types: 1. somatic nerves involved with voluntary movement senses / movement 2. autonomic nerves involved with involuntary movement sympathetic / parasympathetic systems

Cells of the Nervous System Two major cell types: 1. neurons conduct electrical signals 2. glial cells structural & insulating support for neurons

Neuron Structure dendrites axon terminal soma node of Ranvier axon nucleus glial cell

Dendrites Cell body Nucleus Synapse Signal Axon direction Axon hillock Presynaptic cell Postsynaptic cell Myelin sheath Figure 48. 5 Synaptic terminals

Glial Cells

Sensory input Integration Sensor Motor output Effector Figure 48. 3 Peripheral nervous system (PNS) Central nervous system (CNS)

Neuron Signalling How do electrical signals pass through cells? Membrane Potential glial cells provide insulation for electrical impulses to pass through axon glial cell membrane has a lot of lipid molecules called a myelin sheath neurilemma - myelin sheaths wrapped around each other

Glial Cell Node of Ranvier Layers of myelin Axon Schwann cell Axon Figure 48. 8 Myelin sheath Nodes of Ranvier Schwann cell Nucleus of Schwann cell 0. 1 µm

Grey / White Matter Why are brains said to be made of grey and white matter? white matter – neurons with neurilemma grey matter – neurons without neurilemma

Grey / White Matter

Neuron Types

Dendrites Axon Cell body Figure 48. 6 a–c (a) Sensory neuron (b) Interneurons (c) Motor neuron

Neuron Types ganglia

Sensory Neuron also known as afferent neurons carries signals from sensory receptors to the CNS for processing photoreceptors (eyes) chemoreceptors (nose) thermoreceptors (skin) found in clusters of neurons—ganglia

Ganglia

Neuron Types

Interneuron also known as association neurons receives incoming signals from sensory neurons delivers outgoing signals to neurons responsible for responses

Neuron Types

Motor Neuron also known as efferent neurons connected to tissues that respond according what was detected muscle contraction gland secretion

Neuron Responses Does all information detected by your senses go through your brain? reflex arc – connects sensory and motor neurons without going to the brain

Reflex Arc gure 48. 4 2 Sensors detect a sudden stretch in the quadriceps. 3 Sensory neurons convey the information to the spinal cord. Cell body of sensory neuron in dorsal root ganglion Quadriceps muscle 4 The sensory neurons communicate with motor neurons that supply the quadriceps. The motor neurons convey signals to the quadriceps, causing it to contract and jerking the lower leg forward. Gray matter 5 Sensory neurons from the quadriceps also communicate with interneurons in the spinal cord. White matter Hamstring muscle Spinal cord (cross section) Sensory neuron 1 The reflex is initiated by tapping the tendon connected to the quadriceps (extensor) muscle. Motor neuron Interneuron 6 The interneurons inhibit motor neurons that supply the hamstring (flexor) muscle. This inhibition prevents the hamstring from contracting, which would resist the action of the quadriceps.

Neuron Repair Do neurons regenerate? Yes. Peripheral system neurons will repair faster than central system neurons. http: //www. ted. com/talks/ed_boyden. html http: //www. ted. com/talks/alan_russell_on_regenerating _our_bodies. html Homework Section 9. 1 p. 417# 1 – 8