Presentation on theme: "Nervous System & Neurons"— Presentation transcript:
1 Nervous System & Neurons Chapter 29, Section 2Of your textbook
2 Central Nervous System (CNS) Brain & spinal cordBrain – controls complex behaviorSpinal cord -- controls simple responsesReceives information from the peripheral nervous system & interprets it
3 Peripheral Nervous System (PNS) All nerves & neurons outside of the CNS,Cranial nerves (originate in brain)Spinal nerves (originate in spinal cord)Divided into sensory & motor divisions
4 Sensory & Motor Divisions (of PNS) Incoming neurons that convey info from receptors to CNSPicks up info from both internal and external environmentsMotor:Outgoing neurons that convey signals from CNS to muscles & glandsDivided further into the somatic & autonomic systems
5 Somatic vs. Autonomic Nervous System (Motor Division of PNS) Carries signals to skeletal musclesGenerally, controls voluntary actions because it is under conscious controlIncludes reflexesAutonomic:Carries signals to smooth & cardiac muscles, major organ systems and glandsGenerally controls involuntary actions & responses
6 Types of Neurons Sensory Neurons Interneurons Motor Neurons Receive info from inside / outside of bodySend signals to brain / spinal cordInterneuronsLocated in brain / spinal cordRelay info between sensory & motor neuronsMotor NeuronsTake messages from brain / spinal cord to muscles / glands
8 Neuron (animation)The neuron is the structural and functional unit of the nervous systemDendrites: receive information into cell body; highly branchedCell Body: contains the nucleus and organellesAxon: one long extension that transmits an info/impulse away from cell body
9 Neuron Myelin sheath: made of Schwann cells; insulates the axon Nodes of Ranvier: tiny gaps in the myelin sheathAxon terminals, aka synaptic terminals: branched ends of the axonDrag and Drop Quiz – Neuron Structure
10 Neurons and SignalingA neuron uses an electrical signal to transmit messages down its axonA neuron uses a chemical signal – neurotransmitters – to transmit messages across the synapse (either to another neuron or to a muscle / gland)
11 Resting PotentialWhen a neuron is at rest, the inside is negative compared to the outside.There are more sodium (Na+) ions OUTside.There are more potassium (K+) ions INside.
12 Sodium-Potassium Pump Helps the neuron maintain resting potential by pumping Na+ out for every K+ it pumps inUses active transportNeeds energy (ATP)Moves substances against their concentration gradient
13 Action PotentialWhen a neuron is stimulated, membrane channels open & Na+ rushes into the cell.This makes the inside become positive (and the outside becomes negative).
14 An action potential is a moving electrical impulse. It is generated by a stimulus.Na+ enters, and cell becomes positively charged.K+ leaves, and the area of positive charge moves.An action potential only travels one-way down the axon (from dendrites/cell body toward terminals/synapse).Animation
15 An action potential has multiple phases. As the inside of the membrane becomes more positive, it depolarizes.As the inside becomes less positive / more negative, it is repolarizing.
16 An action potential travels faster down a myelinated axon because the impulse jumps from node to node (the gaps along the myelin sheath).
17 Signals at the SynapseWhen the action potential reaches the axon / synaptic terminals, the electrical signal cannot jump the synapse (the tiny gap between one neuron and the next).A chemical signal – in the form of a neurotransmitter – passes from one neuron to another (or onto a muscle or gland).
18 These neurotransmitters stimulate the next cell. If it is another neuron, then that neuron may also have an action potential.If it is a muscle, then the muscle may contract.If it is a gland, then the gland may release a hormone.
19 The neurotransmitters are picked up by special receptor proteins in the post-synaptic cell. When enough neurotransmitters are received, the message is carried forward.Review animationarea of detail