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Coordination in Mammal

Coordination in Mammal. coordination is the way in which receptors detect stimuli, and then nerve impulses are sent to the effectors in mammals, coordination is carried out through the activities of nervous system and the endocrine system.

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Coordination in Mammal

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  1. Coordination in Mammal • coordination is the way in which receptors detect stimuli, and then nerve impulses are sent to the effectors • in mammals, coordination is carried out through the activities of nervous system and the endocrine system

  2. nervous coordination is brought about by transmission of nerve impulses between receptors and effectors through nerve fibres • endocrine coordination is brought about by hormones secreted from endocrine glands

  3. What is Nervous Coordination ? • nervous system of mammal consists of central nervous system(CNS) and peripheral nervous system • CNS includes brain and spinal cord and the peripheral nervous system includes cranial nerves and spinal nerves

  4. Structure of Neurones • neurones make up nervous system in mammal • each neurone has a cell body and nerve fibres • cell body is a mass of cytoplasm with nucleus inside and it is called ganglion • nerve fibres are cytoplasmic processes of neurones and there are two types, one is dendron and the other is axon

  5. dendron transmits nerve impulses towards cell body while axon transmits nerve impulses away from cell body • nerve fibres may be protected by a fatty layer which serves as an insulator to prevent the spread of nerve impulses and help to speed up the rate of transmission

  6. dendron cytoplasm nucleus cell membrane direction of nerve impulses axon nucleus of cell which makes the myelin sheath

  7. sensory neurone Types of Neurones • there are three types of neurones: sensory neurone,motor neurone and association neurone - sensory neurone: transmits nerve impulses from receptor to the central nervous system

  8. motor neurone - motor neurone: transmits nerve impulses from central nervous system to effectors. The axon branches at its end to form many motor end plates which are attached to muscle fibres - association neurone: connects the sensory neurone to the motor neurone and also the neurones in the central nervous system

  9. neurone nerve fibre Nerve • bundles of nerve fibres • usually myelinated and surrounded by a sheath of white connective tissue nerve

  10. impulses do not jump from one fibre to another because of the presence of fatty substance in nerve • in sensory nerves, there may be ganglia where the cell bodies are situated • nerve fibres found inside the central nervous system do not have insulating fatty layers

  11. neurone

  12. Nerve Impulses Transmitted in Nerve Fibre • stimulation of the receptors may initiate nerve impulses and this follows “All-Or-None” principle

  13. ALL impulses are alike regardless of the site from which they are fired off • impulses travel very quickly in one direction from dendron to axon of the same neurone

  14. Nerve Impulses Transmitted across the Synapse • neurones are not in direct contact with each other. A small gap called synapse exist between two neurones • impulses need to jump across the synapse as to travel from one end of axon to dendron of another neurone

  15. Synapses

  16. synapse • ending of axon secretes a chemical which diffuses into synapse and stimulates the next neurone to pass on the impulse • the chemical is unstable and will be destroyed later

  17. presence of synapse enables nerve impulses to travel only from axon of one neurone to dendron of another neurone • it also allows higher level of nervous coordination as one neurone can be linked with a number of other neurones

  18. brain spinal cord Central Nervous System • includes brain and spinal cord in higher animal

  19. skull vertebral column Protection of Central Nervous System • brain is enclosed in cranium of skull while spinal cord is enclosed in vertebral column • CNS is also enveloped in three layers of meninges and between the inner two layers is a cavity filled with cerebrospinal fluid

  20. Functions of Cerebrospinal Fluid • act as a cushion for absorbing external shock • nourish neurones inside as it enables diffusion of oxygen and food to the nerve cells • it also filled up cavity called ventricle in brain and in the central canal of spinal cord • it also helps in preventing collapse of CNS

  21. External view of the brain

  22. cerebrum cerebellum medulla oblongata Parts of Brain brain is divided into three main parts: cerebrum, cerebellum and medulla oblongata

  23. Brain--Cerebrum • lies in the front part of brain and divided into two cerebral hemispheres connected by nerve fibres • surface of cerebrum is highly folded to increase area for coordination • centre of thinking, memory, reasoning, imagination, learning and voluntary actions

  24. motor area association area sensory area • divided into three functional areas - sensory areas: receive impulses from receptors - motor areas: send out impulses to effectors - association area: correlates impulses from different receptors and assists in producing appropriate responses

  25. Brain--Cerebellum • lies below the back part of cerebrum • centre for muscular coordination and involved in control of body balance • damage of cerebellum will lead to a loss of ability to maintain balance

  26. Brain--Medulla Oblongata • lies at the floor of cerebellum • reflex centre for controlling involuntary actions such as breathing, heartbeat, swallowing, coughing, sneezing and salivation • damage of medulla oblongata may lead to death

  27. medulla oblongata Medulla oblongata

  28. Internal Structure of Cerebrum and Cerebellum • outer layer is made up of gray matter which consists of nerve cell bodies • inner layers consist of nerve fibres and is white in colour and is called white matter

  29. Internal Structure of Medulla Oblongata • outer layer is made up of white matter while inner layer is made up of grey matter

  30. Internal Structure of Spinal Cord • arises from medulla oblongata and runs through backbone of mammal • internal distribution of nerve cell bodies is similar to medulla oblongata which the outer cortex contains white matter while the inner cortex is in H-shaped and contains grey matter

  31. white matter grey matter spinal nerve central canal spinal cord • in the central region of grey matter is central canal and filled with cerebrospinal fluid • reflex centre for controlling involuntary actions and it also transmits impulses to and from brain

  32. Grey & White Matters spinal cord & medulla oblongata cerebrum & cerebellum grey matter (cell body) outer region inner region white matter (nerve fibre) outer region inner region

  33. cranial nerve spinal nerve Peripheral Nervous System • consist of cranial nerves and spinal nerves • these nerves leave CNS and run out to every part of the body

  34. Cranial Nerves and Spinal Nerves • Cranial Nerve - twelve pairs of cranial nerves in mammal - most of cranial nerves arise from lateral sides of medulla oblongata • Spinal Nerve - there are 31 pairs of spinal nerves in human

  35. dorsal root ganglion sensory neurone receptor (pain) dorsal root (sensory nerve) association neurone effector(muscle) spinal cord motor neurone ventral root (motor nerve) Spinal Nerve

  36. - all are mixed nerve carrying both sensory and motor neurones - each spinal nerve has a dorsal root and ventral root - dorsal root contains ganglion which contains nerve cell bodies

  37. - cells in dorsal root ganglion are sensory neurones and impulses travel through dorsal root to spinal cord from spinal nerve - ventral root carries motor nerve fibres and their cell bodies are found in H-shaped grey matter of spinal cord

  38. Investigation 15.3 Experiment to Initiate Knee Jerk Reflex

  39. What happens to the leg immediately after tapping? Ans:It kicks up at once.

  40. Does the same action occur again if the knee is tapped the second time? Ans:Yes.

  41. Reflex Action • simple reflex action is a quick, inborn and automatic response of an animal to a stimulus and cerebrum does not involve in the response • protective in function and need not be learnt • same stimulus initiates the same responses at different times • examples like withdrawal from hot objects, blinking, coughing, sneezing and pupil size

  42. Reflex Arc • neural pathway between receptor and effector involved in a reflex action • example is knee jerk reflex Knee Jerk Reflex • At the Receptor • receptor receives stimulus. In this case, tapping stimulates tendon of knee cap

  43. At the Sensory Neurone • from ending of dendrons of sensory neurones, nerve impulses fired off • Across the Synapse to the Motor Neurone • through dorsal root of spinal nerve, impulses are carried to spinal cord

  44. impulses jump across synapses to motor neurones in grey matter but in other reflex action, association neurones may involve • To the effector • impulses are further transmitted through ventral root to effector to produce responses

  45. in knee jerk, effector is muscles in upper leg which it will contract when impulses are received so the leg jerks up and it is an example of spinal reflex action as only spinal cord is involved

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