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Nervous system

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For students to learn about nervous system in Human body.

For students to learn about nervous system in Human body.

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Nervous system Nervous system Presentation Transcript

  • ANALYSING THE ROLE OF THE HUMAN NERVOUS SYSTEM
  • Role of the nervous system
    • It is a communication network
          • It receives information from receptors and then transmits and interprets the information
          • It then formulates appropriate responses to be sent to the effector organs
    • It also controls and coordinates functions throughout the body and helps maintain homeostasis
  • THE HUMAN NERVOUS SYSTEM CENTRAL NERVOUS SYSTEM (CNS) PERIPHERAL NERVOUS SYSTEM (PNS) ORGANISATION OF THE NERVOUS SYSTEM
  • ORGANISATION OF THE NERVOUS SYSTEM Links receptors & effectors to CNS : relays signals between CNS & rest of body HUMAN NERVOUS SYSTEM CENTRAL NERVOUS SYSTEM [CNS] PERIPHERAL NERVOUS SYSTEM [PNS] BRAIN SPINAL CORD CRANIAL NERVES [12 pairs] SPINAL NERVES [31 pairs]
  •  
    • Performs 3 functions:
    • … ..sensory
    • … ..integrative
    • … ..motor
    THE ROLE OF THE NERVOUS SYSTEM
  • AN OVERVIEW OF THE FUNCTIONS OF THE NERVOUS SYSTEM Sensory receptors detect stimuli from int. & ext. environments & initiate nerve impulses carrying information to CNS CNS processes & integrates information by analysing & storing some of it, & then make decisions to initiate suitable responses Motor commands from CNS transmitted to effectors [muscles or glands] to carry out responses 1 3 2
  • THE HUMAN BRAIN HUMAN BRAIN HYPOTHALAMUS THALAMUS MEDULLA OBLONGATA CEREBELLUM CEREBRUM
  • THE HUMAN BRAIN SKULL MEDULLA OBLONGATA CEREBELLUM CEREBRUM VERTEBRA SPINAL CORD PITUITARY GLAND THALAMUS HYPOTHALAMUS
  •  
  • THE BRAIN
  • Medulla oblongata Pons Brainstem Cerebellum Cerebrum Thalamus Hypothalamus STRUCTURE OF THE BRAIN
    • The cerebrum is the largest and most complex part of the brain.
    • It is divided into two halves called the cerebral hemispheres.
    • The left hemisphere controls the movements on the right side of the body.
    • The right hemisphere controls the movements on the left side of the body.
    • The cerebrum is the centre which receives the sensory input and carries out integrative functions before initiating appropriate motor responses.
    • It also coordinates the activities of the other parts of the brain.
    • The outer region of the cerebrum is the cerebral cortex.
    • The cerebral cortex is a structure with many folds which increases the surface area.
    • The cerebral cortex directs voluntary muscle movements , which result in a sensory perception that is, when a person becomes aware of what he sees, hears, smells, tastes or touches.
    • It is also responsible for many mental abilities such as learning, memorising, reasoning, language skills, speech. mathematical skills, imagination, artistic talent and personality traits.
    • Brain damage from trauma, a stroke or a tumour can result in specific defects, such as speech impairment. reading difficulty, or the paralysis of certain parts of the body.
    CEREBRUM
    • The cerebellum is located below the cerebrum near the top of the spinal cord.
    • The cerebellum is the coordinating centre for body movement
    • The cerebellum receives information from the sensory receptors on the positions of different parts of the body; and, from the cerebrum, an indication of the need to move.
    • The cerebellum evaluates the information and relays the need for coordinated movements back to the cerebrum.
    • The cerebrum then sends appropriate commands to the muscles
    • The cerebellum controls voluntary muscles, posture, balance and the coordination of walking, running and playing sports
    CEREBELLUM
  • MEDULLA OBLONGATA
    • The medulla oblongata regulates the internal body processes that do not require conscious effort, that is, automatic functions such as the heartbeat, breathing and vasoconstriction
    • It is also the reflex centre for vomiting, coughing. sneezing, hiccupping and swallowing.
    • NOTE: THE BRAINSTEM [connects the brain & spinal cord]- MADE UP OF PONS & MEDULLA OBLONGATA
    HYPOTHALAMUS
    • The hypothalamus plays an important role in homeostatic regulation . It acts as a major coordinating centre for regulating sleep. hunger, thirst, body temperature, water balance and blood pressure.
    • It is also the control centre of the endocrine system .
    • The pituitary gland secretes hormones that influence other glands and body functions.
    • The hypothalamus controls the release of several hormones from the pituitary gland and thereby serves as an important link between the nervous and endocrine systems .
    PITUITARY GLAND THALAMUS
    • The thalamus is responsible for sorting the incoming and outgoing information in the cerebral cortex.
    • It also integrates the information from the sensory receptors to the cerebrum by enhancing certain signals and blocking others
  • THE SPINAL CORD AND ITS MAIN FUNCTIONS INTERNEURONE DORSAL ROOT DORSAL ROOT GANGLION AFFERENT NEURONE RECEPTOR EFFECTOR EFFERENT NEURONE CENTRAL CANAL GREY MATTER [ contains cell bodies] SPINAL NERVE WHITE MATTER {contains myelin-coated axons] VENTRAL ROOT CROSS SECTION OF THE SPINAL CORD
    • The spinal cord is contained within the vertebral column
    • The spinal cord is surrounded by cerebrospinal fluid which acts as a shock absorber and provides the spinal cord with nutrients.
    • It consists of white matter and grey matter.
    • (a) In cross section, the grey matter looks like a butterfly or the letter H.
    • (b) The grey matter consists mainly of cell bodies of neurones.
    • (c) The grey matter is surrounded by the white matter .
    • (d) The white matter comprises myelin-coated axons of neurones that extend the whole length of the spinal cord.
    THE SPINAL CORD AND ITS MAIN FUNCTIONS
  • The spinal nerves emerge from the spinal cord through two short branches or roots. (a) The dorsal root contains the axons of the afferent neurones which conduct nerve impulses from the sensory receptors to the spinal cord. (b) The cell bodies of the afferent neurones are clustered in the dorsal root ganglion (c) The ventral root contains the axons of the efferent neurones which conduct nerve impulses away from the spinal cord to the effectors. (d) The dorsal and ventral roots join to form a spinal nerve. FUNCTION : The spinal cord (a) processes certain types of sensory information and sends out responses via the efferent neurones. (b) contains neurones that convey signals to and from the brain, (c) contains the neural pathway for reflexes
  • THE NEURONE
    • The nervous system is made up of millions of nerve cells called neurones
    • Neurones transmit nerve impulses to other nerve cells, glands or muscles.
    • There are three types of neurones
    THE NEURONE
    • Carry sensory information from receptors cells to the brain & spinal cord
    Structure of an afferent (sensory) neurone
    • Carry sensory information from brain & spinal cord to the effectors
    • [muscle / gland cells]
    Structure of an efferent (motor) neurone
    • Convey nerve impulses between the various parts of the brain and spinal cord
    • Transmit nerve impulses between the afferent neurones and efferent neurones
    • Transmit nerve impulses from one side of the spinal cord to the other side, or from the brain to the spinal cord and vice versa
    • Many of the neurones that carry out integrative functions are the interneurones and the efferent neurones respond to these integrative signals
    Structure of an interneurone
  • STRUCTURE OF AN EFFERENT NEURONE
    • Dendrites are fibres that receive information or signals from other neurones or from the external environment and conduct them towards the cell body.
    • Dendrites of afferent neurones have special membrane adaptations that allow them to produce signals in response to specific stimuli from the external environment such as pressure, light or heat.
    • A long, thin fibre called the axon extends outward from the cell body.
    • • The axon conducts the nerve impulses away from the cell body.
    • • The axons are usually bundled together into nerves
    • Nerve impulses are conducted along the axon and finally reach the synaptic terminals [swellings at the branched ends of the axons] located at the far end of each axon.
    • • The synaptic terminals then transmit these signals to the muscle cells, gland cells or the dendrites of another neurone.
    • The electrical signals or nerve impulses then travel along the dendrites and converge on the cell body of the neurone.
    • • The cell body has a nucleus and other organelles which are found in cells.
    • • The cell body integrates the signals and coordinates the metabolic activities.
    • Some axons are insulated by a thick coat of material called a myelin sheath .
    • This sheath protects and insulates the axons, and helps to speed up the transmission of the nerve impulses.
    dendrite Cell body Myelin sheath Muscle fibre (effector) Synaptic terminals axon Direction of nerve impulse nucleus 1 4 3 2 5
  • THE TRANSMISSION OF INFORMATION ALONG THE NEURONE
    • The transmission of information along the neurone is through electrical signals known as nerve impulses .
    • An impulse is a wave of positive charges that travel along the axon to the synaptic terminal.
    • A neurone will not transmit an impulse unless the stimulation is strong enough.
    • Once the magnitude or size of the stimulation reaches a threshold level, a full-sized impulse is generated to travel the entire length of the axon.
  • The transmission pathway of information Reception of stimuli by receptors Response by the effectors From the CNS to the effectors Integration & interpretation by the central nervous system From receptors to the central nervous system 1 5 4 3 2
  • Afferent neurone Efferent neurone Interneurone 1 5 4 3 2 6 Receptors in the ear Muscles in the arm Receptors in the ear pick up the ringing of the doorbell. The nerve impulses pass from the afferent neurones to the interneurones in the brain The receptors trigger nerve impulses in the afferent neurones. From the interneurones, nerve impulses are transmitted to the efferent neurones and then to the muscles The brain interprets the nerve impulses from many interneurones that the doorbell is ringing. The brain also decides that the door should be opened The muscles in the arm carry out the response and open the door 1 2 3 4 5 6 The transmission pathway of information
  • The transmission of nerve impulses along the three types of neurones Synaptic terminal dendrites axon dendrite Cell body receptor in skin axon myelin sheath Synaptic terminal on muscle fibre Cell body Cell body axon myelin sheath Efferent neurone synaptic terminal Afferent neurone Interneurone
  • DIFFERENCE BETWEEN STRUCTURE OF AFFERENT NEURONE & EFFERENT NEURONE AFFERENT NEURONE EFFERENT NEURONE Long dendrite, short axon Short dendrite, long axon Cell body at the side of the neurone [not at the end] Cell body at the end of the neurone Begins with receptor Ends with effector
  • TRANSMISSION OF INFORMATION ACROSS SYNAPSES