UNIT THREE BIOLOGY AREA OF STUDY #2: DETECTING & RESPONDING EXAM REVISION LECTURE CHP 6: COORDINATION & REGULATION NERVOUS SYSTEM
CHP 6 TOPIC 1: THE NERVOUS SYSTEM The nervous system is divided into two parts; the Central Nervous System (CNS) and the Peripheral Nervous System (PNS)
CHP 6 TOPIC 1: THE NERVOUS SYSTEM NERVOUS SYSTEM Peripheral Central Somatic Autonomic Brain Spinal Chord Sensory Motor Sympathetic Parasympathetic
Central Nervous System Peripheral Nervous System CHP 6 TOPIC 1: THE NERVOUS SYSTEM
CHP 6 TOPIC 1: THE NERVOUS SYSTEM CENTRAL NERVOUS SYSTEM Brain Dilates pupil Stimulates salivation Salivary glands Relaxes bronchi Spinal cord Lungs Accelerates heartbeat Heart Inhibits activity Stomach Pancreas Stimulates glucose Liver Adrenal gland Secretion of adrenaline, nonadrenaline Kidney Relaxes bladder Sympathetic ganglia Stimulates ejaculation in male SYMPATHETIC • “ Fight or flight” response • Release adrenaline and noradrenaline • Increases heart rate and blood pressure • Increases blood flow to skeletal muscles • Inhibits digestive functions
CHP 6 TOPIC 1: THE NERVOUS SYSTEM CENTRAL NERVOUS SYSTEM Brain Contracts pupil Stimulates salivation Constricts bronchi Spinal cord Slows heartbeat Stimulates activity Stimulates gallbladder Gallbladder Contracts bladder Stimulates erection of sex organs PARASYMPATHETIC • “ Rest and digest ” system • Calms body to conserve and maintain energy • Lowers heartbeat, breathing rate, blood pressure
CHP 6 TOPIC 1: THE NERVOUS SYSTEM The Brain Note: meninges (membranes) surrounding the CNS tissue (not myelin!) and fluid between the tissue and meninges helps to cushion the CNS from knocks
Topic CHP 6.1 Questions: • What does and EEG (electroencephalogram) measure? __________________________ • Name three things that protect the brain and spinal cord from physical shock? _________________________, _______________________, ______________________ • What part of the brain is the control centre for temperature maintenance, water balance and blood pressure? __________________________________ • True/ False: the thalamus receives impulses from motor neurons and directs them to the various parts of the brain where they are interpreted? • The folded surface of the cerebrum (largest part of the brain) is called what? __________________ _________________ • Which part of the nervous system would be involved in the following transmissions: • Information from the eye to the CNS via: Somatic or Visceral neurons • From the skin: Somatic or Visceral neurons • From the heart: Somatic or Visceral neurons • To the heart to increase heart rate: ________________________ • To the heart to decrease hearts rate: _______________________ • To the effector muscles of the arm: _________________________ • To blood vessels to constrict blood flow: ____________________ / 12 Marks
CHP 6 TOPIC 2: NEURONS The nervous system of complex animals receives and carries information (stimulus) from receptors, processes (control centre) responses and directs (to effectors) those responses. In order to achieve these functions the nervous system contains many types of specialised cells, known as neurons.
CHP 6 TOPIC 2 NEURONS Dendrites Cell Body Axon
CHP 6 TOPIC 2 NEURONS Neurons: • Specialised cells which make up the nervous system are called neurons • a typical neuron has: • dendrites: highly branched extensions of the cell body that receive and then carry information towards the cell body • a nucleus within the cell body • an axon: an extension that carries information away the cell body to the axon terminals (transmit chemical messages to other neurons or effectors) • the presence of the myelin sheath, lipid protein based (on affector and effector neurons) increases the rate at which a nerve impulse is conducted along the axon. Myelin sheath is composed of Schwann cells wrapped around the axon. • Three types of neurons: • sensory (affector) neurons: (PNS -cell body roughly central on the axon) • connecting (inter) neurons: (CNS - found in the CNS, contains many connections to other cells) • motor (effector) neurons: (PNS - cell body is at the site of the dendrites, adjacent to CNS)
CHP 6 TOPIC 2 NEURONS Cells of the nervous system. (a) A typical sensory neuron (b) A typical motor neuron (c) Structure of a nerve (d) A typical connector or inter neuron
Myelination CHP 6 TOPIC 2 NEURONS • Schwann Cells • Act as insulators to the nerve • Lipo-protein based • Separated by Nodes of Ranvier Node of Ranvier
Myelination cont CHP 6 TOPIC 2 NEURONS • Schwann Cell • Speed up conduction of impulse • Depolarization skips from one node to another.
Synapse CHP 6 TOPIC 2 NEURONS • Receptor site receives neurotransmitters • Neurotransmitters change permeability of membrane. • Ions flood into membrane setting off a action potential in post-synaptic cell. • Position of neurotransmitter substances (ends of axons) ensures that nerve impulses are transmitted on one direction only: from an axon to another neuron, muscle or gland.
The Structure of a Synapse. CHP 6 TOPIC 2 NEURONS
Reflex Arc CHP 6 TOPIC 2 NEURONS • Acts in an “emergency response” • Cuts time of response.
Reflex Arc CHP 6 TOPIC 2 NEURONS • Sensory Neuron • Interneuron • Motor Neuron • Create reflex arc
Topic CHP 6.2 Questions: • Name the two types of neurons of the PNS: ________________, __________________ • Name a distinctive feature of a sensory neuron that differs from: • A connecting/ interneuron: _________________________________________________ • A motor neuron: __________________________________________________________ • True/ False: Myelin sheath is made of phospholipids • True/ False: Neurons are responsible only for electrical impulses and not chemical messengers • Name two features of a neuron that would speed up electrical impulses: • __________________________________ ii. ______________________________________ • (Fill in gap) Axon terminals forms_____________ with other neurons or with ___________________ • Another name for an effector neuron is: ____________________ • A very simple involuntary nervous response such as lifting of the foot from a painful stimulus is known as a: ___________________ • Acetylcholine is an example of ______________________ substance and is found in the brain and PNS at neuromuscular junctions. • True/ False: vesicles containing transmitter substances occur only at the ends of axons / 10 Marks
Resting Potential CHP 6 TOPIC 3 NERVE IMPULSES Cells are set up as electrically polarized. • They are in “resting state” • Ready to do work. • A more + charge outside the cell than inside • Created by Na+/K+ pumps
CHP 6 TOPIC 3 NERVE IMPULSES ACTION POTENTIAL • These resting neurons are easy to knock off balance • Electrical, chemical, or mechanical stimulus can move them to an action state. • Once the “threshold” level is met, signal is sent.
CHP 6 TOPIC 3 NERVE IMPULSES • as an impulse moves along an axon, the permeability of the membrane changes so that positive Sodium ions (Na+) move into the neuron through ion channels • the change in permeability moves along the neuron • Sodium ions (NA+) move into the neuron causing a change in polarity (from negative to positive). Potassium ions (K+) move out of the neuron (momentarily). When Na+ and K+ are momentarily together inside the neuron, the charge is positive • after a nerve impulse has passed along the membrane, the original distribution of ions across the membrane is restored • the larger the axon’s diameter, the faster the impulse moves along it • the presence of myelin increases the speed of an impulse (it also insulates one neuron from another!) • Multiple sclerosis is an example of a disease caused by damaged myelin sheath • an unstimulated nerve is said to have ‘resting potential’ an activated nerve has ‘action potential’ (the wave being the action potential)
CHP 6 TOPIC 3 NERVE IMPULSES Networks of nerve cells • neuron pathways are of two kinds: diverging or converging • diverging pathway: a single axon of one neuron branches and links up wit a larger number of postsynaptic neurons. • converging pathway: many presynaptic nerves come together to influence a smaller number of synaptic neurons, ultimately one. • one advantage of the convergence system is that one cell can have multiple signals that influence an outcome. • In a multi pathway system of signaling messages, some may be excitatory and others may be inhibitory. It is the balance between excitatory and others may be inhibitory that determines the kind of signal or whether a target cell receives any signal
Topic CHP 6.3 Questions: • True/ False: In a ‘resting state’ Na+ ions are in greater concentration outside the neuron than inside • In a ‘resting state’, the outside of the neuron is: positively/ negatively charged • Name two things that can stimulate a dendrite of an afferent neurone: __________________, & __________________________ • Name two things that neurotransmitter can do to a target cell: __________________ & _______________________ • True/ False: the smallest amount of neurotransmitter substance is enough to start an action potential • True/ False: Na+ and K+ dissolve through the lipid bilayer passively • In less than ten words, what is meant by membrane depolarisation: ____________________ ___________________________________________________________________________ • What is the charge of a ‘resting cell’: +70 millivolts/ -70 millivolts • Name one disease caused by ineffective myelin: ________________ / 9 Marks
CHP 6 TOPIC 4 SIGNAL TRANSDUCTION • signal transduction is the process by which a cell converts one kind of signal into another by a series of relay molecules • signals initiating transduction include: • hormones • neurotransmitters • neurohormones • environmental stimuli (i.e. light- photosynthesis!) • cellular responses to transduction include: • activation of a gene- protein production • alteration of cellular activity, such as • increased cellular secretions • Changes in cell permeability • Increased rates of chemical reactions
Across A Synapse CHP 6 TOPIC 4 SIGNAL TRANSDUCTION
Principles of cell communication CHP 6 TOPIC 4 SIGNAL TRANSDUCTION
CHP 6 TOPIC 4 SIGNAL TRANSDUCTION neurotransmitters (being protein-based) cannot pass through the plasma membrane; they interact with a receptor on the cell surface.
CHP 6 TOPIC 4 SIGNAL TRANSDUCTION Fatty-acid-derived hormones pass through the plasma membrane and combine with a cytoplasmic receptor, which then passes into the nucleus where they directly activate or suppress particular genes.
CHP 6 TOPIC 4 SIGNAL TRANSDUCTION Neurohormones • are chemicals released directly into the blood • travel to a target organ where the signal is transduced and the receptor cells respond • neurons in the hypothalamus of the brain has several different neurohormones. These are released into the blood and travel to the pituitary cells, both anterior and posterior, where they exert their effect Examples: thyrotropin-releasing hormone (TRH) signals anterior pituitary cells to produce thyroid stimulating hormone (TSH); This is an example of the nervous and endocrine systems interacting together Other examples: thyroptropin releasing hormone (TRH); thyroid stimulating hormone (TSH); corticotropin releasing hormone (CRH)
Topic CHP 6.4 Questions: • Pituitary cells, both anterior and posterior are target cells for a number of different neurohormones. Name one neurohomrone that targets the pituitary and identify where it is produced (source): Name: ___________________ Source: ________________________ (2 marks) • Define signal transduction: __________________________________________________ _________________________________________________________ ________________ • What is a hormone? • List three possible cellular responses to signal transduction:____________________________, ____________________________, ____________________________ • What kind of cells produce neurohormones? _____________________________________ • What kind of cells are the target of: (1 mark each) • neurohormones: ________________________________ • Neurotransmitters: ______________________________ • Insulin: ________________________________________ • Glucagon: ______________________________________ • Interleukin-1: ___________________________________ • List three types of substances that are transduced: __________________, _____________, _____________________________ • True/ False: all messengers pass through target cell membranes to induce a response from the target cell • True/ False: motor neuron axon terminals never touch another neuron but can physically connect with muscles and glands • Neurotransmitter substances move faster/ slower than electrical impulses and quickly/ slowly digested by enzymes of the body • What term is used to describe the amount of neurotransmitter substance that is enough to result in an electrical charge from a postsynaptic dendrite: _______________________ /14 Marks
Paracrine glands • Endocrine glands • Exocrine glands