Module 5 Communication, homeostasis & energy Block 2C – 5.5 Animal responses 5.5.5 The nervous system

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Learning Objectives Success Criteria To understand what affects the transmissions of action potentials Outline why animals need to respond to the environment (Grade E - D) Outline the organisation of the nervous system (Grade C –B) Outline the roles of the autonomic nervous system (Grade B – A) 3

Starter – 2 marks each. Question 1 Question 2 Saxitoxin is a chemical that blocks voltage gated sodium ion channels. What effect is it likely to have on the nervous system? Guillane-Barre syndrome is an auto-immune disease whereby the myelin sheath around certain neurones is damaged. How does this result in muscle weakness and paralysis? Sodium ions unable to diffuse into the neurone through the channels. Neurone will not be depolarised so no action potentials Conduction of impulses slower – similar effect to an unmyelinated neurone. Nerve impulse may be conducted more slowly or not at all

Why animals need to respond to the environment. Write down one reason on your paper why animals need to respond to the environment. Pass your paper to your neighbour, repeat. Rapid response and coordinated for survical. Control of balance, posture, temp regulation co ordination with endocrine system. 1. Detecting any change in the environment 2. cell signalling to occur between parts of the body 3. coordination of a range of effectors to carry out reponses 4. suitbale responses

The Nervous System Major division - Central vs. Peripheral Central Nervous System Peripheral Nervous System Major division - Central vs. Peripheral Central or CNS- brain and spinal cord Peripheral- nerves connecting CNS to muscles and organs CNS – human brain = 86 billion neurones= most =relay neurones (lots of connections) non-myelinated cells-grey = grey matter Spinal cord = many non myelinated relay neurones – central grey matter and also myelinate neurones- outer region=white matter. Myelinated = carry Aps up and down the spinal cord long distance and fast. Between each vertebrae- peripheral nerves enter and leave spinal cord carrying Aps to and from the rest of the body

Peripheral Nervous System 3 kinds of neurons connect CNS to the body sensory motor interneurons Motor - CNS to muscles and organs Sensory - sensory receptors to CNS Interneurons: Connections Within CNS Role = rapid communication between sensory-CNS-effectors Spinal Cord Brain Nerves A nerve is a bundle of nerve cells encased in a nerve sheath while a neurone is a single nerve cell.

Organisation of the nervous system – draw a flow chart to summarise the below: The mammalian nervous system is composed of two systems. The central nervous system and the peripheral nervous system. The PNS consists of all the neurones that connect the CNS to the body, divided into two groups, the sensory nervous system and the motor system. The motor system is further divided into the somatic nervous system and the autonomic nervous system. One is under conscious control, for voluntary actions and the other is under subconscious control – involuntary actions. This is further subdivided by function into two groups; parasympathetic and sympathetic nervous systems. An increase in activity is associated with the sympathetic nervous system and a decrease in activity is parasympathetic.

Peripheral Nervous System k e l t a ( o m i c ) y p h P r s A u n N v Use pages 90-92 to add to flow chart the roles of autonomic nervous system

Somatic System Nerves to/from spinal cord control muscle movements somatosensory inputs Both Voluntary and reflex movements Skeletal Reflexes simplest is spinal reflex arc Muscle Motor Neuron Interneuron Skin receptors Sensory Brain Conscious control Neurones mostly myelinated=rapid

Autonomic System Two divisions: Sympathetic Parasympatheitic Referred to as antagonistic systems in many cases the action of one system opposes the action of the other. Under normal resting conditions, impulses are passing along the neurones of both systems at a low rate. Changes to internal conditions, alter the balance of stimulation between 2 systems, which leads to a response Control involuntary functions Can be influenced by thought and emotion Autonomic – self governing, controls homestatic mechanisms. Mostly nonmyelinated neurons . Examples Glands, cardiac muscle, smooth muscle in blood vessels, airways and digestive system.

The Autonomic Nervous System The system can have different effects on the same kinds of muscles because the motor neurones involved secrete different kinds of neurotransmitters at the synapses. Sympathetic NS uses noradrenaline Parasympathetic NS uses acetylcholine

Sympathetic “ Fight or flight” response CENTRAL NERVOUS SYSTEM Brain Spinal cord SYMPATHETIC Dilates pupil Stimulates salivation Relaxes bronchi Accelerates heartbeat Inhibits activity Stimulates glucose Secretion of adrenaline, nonadrenaline Relaxes bladder Stimulates ejaculation in male Sympathetic ganglia Salivary glands Lungs Heart Stomach Pancreas Liver Adrenal gland Kidney “ Fight or flight” response Release adrenaline and noradrenaline Increases heart rate and blood pressure Increases blood flow to skeletal muscles Inhibits digestive functions keywords: sympathetic nervous system; fighlt or flight response

Parasympathetic “ Rest and digest ” system CENTRAL NERVOUS SYSTEM Brain PARASYMPATHETIC Spinal cord Stimulates salivation Constricts bronchi Slows heartbeat Stimulates activity Contracts bladder Stimulates erection of sex organs Stimulates gallbladder Gallbladder Contracts pupil “ Rest and digest ” system Calms body to conserve and maintain energy Lowers heartbeat, breathing rate, blood pressure key words: parasympathetic nervous system; rest and digest system

Plenary – comparison of autonomic nervous system Organ Sympathetic System Parasympathetic System Eye Tear glands Salivary glands Lungs (Bronchi) Heart rate Gut (digestion) Liver (chemicals produced) Bladder Blood vessels Sweat glands Dilates pupil No effect Inhibits saliva production Dilates bronchi Speeds up heart rate Inhibits peristalsis Stimulates glucose production Inhibits urination Vasoconstriction Secretion of sweat Constricts pupil Stimulates tear secretion Stimulates saliva production Constricts bronchi Slows down heart rate Stimulates peristalsis Stimulates bile production Stimulates urination

Plenary - answers Organ Sympathetic System Parasympathetic System Eye Tear glands Salivary glands Lungs Heart Gut Liver Bladder Blood vessels Sweat glands Dilates pupil No effect Inhibits saliva production Dilates bronchi Speeds up heart rate Inhibits peristalsis Stimulates glucose production Inhibits urination Vasoconstriction Secretion of sweat Constricts pupil Stimulates tear secretion Stimulates saliva production Constricts bronchi Slows down heart rate Stimulates peristalsis Stimulates bile production Stimulates urination

Keywords Neurons that receive information from our sensory organs (e.g. eye, skin) and transmit this input to the central nervous system are called afferent neurones. (think a – into brain) Neurons that send impulses from the central nervous system to your limbs and organs are called efferent neurones. (think e – to receptors) Ganglia are the clusters of cell bodies typically linked by a synapse. Ganglia contain the cell bodies of afferent neurones.

Progress check State and explain why breathing, which is an involuntary response, can also be controlled by the somatic nervous system.(2) Sort these into those which are controlled by the somatic ns and those by the autonomic ns (2) Pupil dilation, throwing a ball, blood pressure, walking

Answers Breathing can be controlled when you (eg) swim underwater (1) to prevent water from entering the lungs (1) Somatic – throwing a ball, walking (1) Autonomic – pupil dilation, blood pressure (1)

Compare and contrast the sympathetic and parasympathetic systems Refer to: length of pre and post ganglionic neurones, location of ganglions, neurotransmitter used, general action of the system, action at most active times Compare and contrast the sympathetic and parasympathetic systems Just outside CNS Each lead to separate effector In the effector tissue

Compare and contrast

Why does the sympathetic nervous system inhibit digestion? Plenary Why does the sympathetic nervous system inhibit digestion? What changes are made in your body when you walk down a quiet road late at night and you think that you’re being followed? The sympathetic system prepares the body for activity – oxygen and nutrients must be supplied to the muscles. Therefore blood is diverted towards the muscles and away from the digestive system. Increase in: heart rate, stroke volume, breathing rate, depth of breathing, blood pressure. Diversion of blood towards muscles.

Learning Objectives Success Criteria To understand what affects the transmissions of action potentials Outline why animals need to respond to the environment (Grade E - D) Outline the organisation of the nervous system (Grade C –B) Outline the roles of the autonomic nervous system (Grade B – A) 24