Presentation on theme: "Biology 30 NERVOUS SYSTEM"— Presentation transcript:
1Biology 30 NERVOUS SYSTEM 1. Nervous System Overview2. The Neuron3. Reflex Arc4. The Action Potential5. The Synapse / Neurotransmitters6. Nervous System Diseases7. Drugs8. PNS9. CNS10. The Brain
2General Functions 4. Transmission Reception 2. Conduction 3. Interpretation and Organization4. TransmissionThe nervous systems main function is to maintain homeostasis: a maintenance of the internal environment i.e. pH, body temp, glucose levels, BP, water levels, etc
4The Neuron- The functional unit of the nervous system, it conducts nerve impulses There are 3 kinds of neurons:1) sensory neurons (afferent)- take impulses from the body receptors to the CNS2) motor neurons (efferent)-take impulse away from the CNS and to the muscles and glands3) interneurons- are actually in the CNS (in the brain and spinal cord)***Neuroglia (glial cells)- supportive cells that aid the interneurons of the brain. Nourish neurons, removes waste from neurons, and protect neurons.
6The Neuron has 3 basic Basic parts: 1) cell body- nucleus and cytoplasm2) Dendrites-finger-like projections of cytoplasm of cell body. They receive information3) Axon-extension of cytoplasm. Transmit impulse away from the body
8Some neurons contain the following additional parts: Myelin Sheath-a white fatty covering that insulates the axon. Schwann cells produce the myelin sheathSchwann cells- a special kind of glial cell that produces a myelin sheath that wraps around the axons as insulationOn top of protection, the myelin sheath allows for faster conduction of impulses and greater power of regenerationThe myelin sheath is NOT continuous but rather forms intermitted gaps called the Nodes of Ranvier. Impulses will now ‘jump’ from Node to Node rather then slowly moving through the entire length of the axon. (faster impulses)
10All nerves of the PNS, as well as all motor and sensory neurons are myelinated, only some of the nerves in the CNS are myelinatedNon- Myelinated neurons in the brain= grey matterMyelinated nerves in the brain are called white matter
13NervesIndividual neurons are organized into tissues called nerves.
14Repairing Damaged Nerves Nerves in the PNS are surrounded by a thin membrane called the neurilemma which helps to regenerate damaged axonsNerves in CNS lack neurilemmas and cannot be repairedArea of research: stem cells, brain band-aid
15Reflex Arcautomatic, quick, involuntary responses to internal or external stimuli.does not immediately involve the brain.allows quicker reaction times to a potentially harmful stimulus
175 Components of a Reflex Arc: 1. Sensory receptor -senses something2. Sensory neuron -sends signal to the CNS3. Interneuron- registers signal4. Motor neuron -sends response back5. Effector- caries out the action
18Action Potential A nerve impulse is an action potential An action potential is an electrochemical event with a rapid change in polarity (relative electrical potential) down a nerve cell that results in the conduction of a nerve impulse.
19Steps of a Nerve Impulse (Action Potential 1. Resting Potential Polarization: voltage difference of -70mV across a nerve cell membranecaused by the sodium potassium pump (gate): more sodium is pumped out than potassium is pumped in, resulting in a negative charge inside the axon of the neuron
20also potassium moves out by diffusion more easily than sodium moves in Result: excess positive charge outside the membrane and negative charge inside the membrane
212. Stimulation / Depolarization A threshold stimulus must be applied (a change in pH, pressure, or an electrical stimulus) This causes the sodium potassium pump to cause Na+ gates to open and tons of Na+ rush into the cell, and small amounts of K+ to move outmembrane becomes depolarized (+ 40 mV)
223. Re-polarizationAfter the wave of impulse has move through Na+ gates close to stop inflowchange in electrical potential causes K+ channels to open and K+ ions rush out of the cell
23Restores the polarized state but now is hyperpolarized – more positively charged on the outside than the resting state (over-shoot)(also the ion concentrations are reversed from the resting state )
244. Refractory periodresting potential (-70mv) must be restored before the neuron can fire againNa+ are pumped out and K+ are pumped back into the cell using ATP energy.The
26The Action Potential in Action Neuron Action PotentialPropagation
27Saltatory Actionthe speed of the nerve impulse is increased by jumping from node of Ranvier to node of Ranvier (gated channels are found only at the nodes)Propagation of the Action Potential
28Threshold level – minimum depolarization that must be reached (usually around +30mV) before sufficient Na+ gates open to continue the action potentialAll or None Response – if the threshold level is not reached, the action potential will not occur at all. If the threshold is reached or exceeded a full action potential will result.The wave of depolarization is self propagating, meaning that it will continue without any aid until its passed on to the next neuron
29How do we differentiate intensity? Ex hot vs warm?
30Intensity is determined by: 1. the number of neurons that fire simultaneously2. the frequency at which the neurons fire3. the threshold level of different neurons (lower threshold neurons are more likely to fire, and are found in more “sensitive” areas)
31The Synapse and Neurotransmitters Neurons are NOT physically attached to each other, but are separated by a gap (synaptic cleft), the electrical impulse cannot just simply cross the gap to the next dendrite, something is neededNeurotransmitters are stored in synaptic vesicles of the axon and are released to carry the information across this synaptic gap
33Structures in the Synapse Pre-synaptic membrane – membrane found at the synaptic ending of the neuron sending informationPost-synaptic membrane- membrane found at the dendrite of the neuron receiving informationSynaptic cleft – space between the pre and post synaptic membranes.
34Neurotransmitters continue the impulse across the synaptic cleft Crossing the impulse across the gap is a chemical reaction1) The end of pre-synaptic axon contains vesicles that have specialized neurotransmitters (NTs), as the impulse gets to the end of the axon the NTs are released in to the gap2) The NTs diffuse across the gap and attached to specialized receptors found on the post synaptic dendrite.3) The wave of depolarization continues on the through the next neuron
35Neurotransmittersexcitatory neurotransmitters – cause the opening of Na+ channels to cause depolarization
36-inhibits action potentials 2. inhibitory neurotransmitters –block Na+ channels and open K+ channels ions which causes hyper-polarization-inhibits action potentials
37Summation – at any given time there are many neurons acting and releasing NTs into the synaptic cleft, the net effect of excitatory and inhibitory neurotransmitters is called summationONLY if there is adequate excitation to reach the threshold, the neuron will fire.
38-may require more than one neuron to release neurotransmitters
39A response may involve both excitatory and inhibitory neurotransmitters Ex) Throwing a ball: Triceps contracts and bicep relaxes
40Integration – the degree of sensation felt or the degree of response created by the brain depends on the number of neurons that fire
41There are 9 universally recognized neurotransmitters: aspartate, glycine, GABA, glutamate, dopamine, nor-epinephrine, epinephrine, seratonin, and acetylcholine.
42Some of the more common neurotransmitters (and their enzymes) include: Function of NeurotransmitterAcetylcholineCholinesteraseInvolved with muscle contraction of the skeletal musclesDopamineMonoamine oxidase enzymeResponsible for voluntary movement and emotions of pleasureSerotoninRegulates temperature, sensory perception, sleep and involved in mood stabilization and controlNor-epinephrineRegulates the stress “fight or flight” responseGABAInhibitory action of motor behavior
43Removing Neurotransmitters To be effective, the NTs must NOT linger around in the gap, other wise successive impulses will occur. NTs are removed from the gap by:1. Degradation by enzymes in the synaptic cleft2. Re-uptake by the pre-synaptic membrane3. Diffusion out of the synaptic cleft4. Inability to bind due to competitive inhibitors
44The Effects of DrugsDrug – anything that is not food that alters the normal bio-chemistry of the body in some way.
45Stimulant – mimics neurotransmitter, decreases rate of breakdown of neurotransmitter or increases release of neurotransmitterDepressant – blocks receptor site, decreases production of neurotransmitter, or increases the breakdown of neurotransmitter
46Alcohol: - depressant -seems to enhance GABA -leads to lack of coordinated response, and loss of normal social inhibitions.-may also weaken the effect of glutamine, an excitatory neurotransmitter, leading to sluggishness and lack of co-ordination.Close to Home Animation: Alcohol
47Marijuana:- a depressant and hallucinogen-acts on the canniboid receptors of the brain that affect concentration, perception and movement.-may have an impact on the activity of seratonin, GABA and norepinephrine in the brainnot physically addicting, however this is a gateway drug and may be psychologically addicting
48Cocaine:-a stimulant-blocks the re-uptake of dopamine, causing an adrenaline like effect from the dopamine-as dopamine levels increase in the synapse, the body produces less, thus making cocaine very physically addictingClose to Home Animation: Cocaine
49Crystal meth:-a stimulant-passes directly through neuron membranes and causes excessive release of dopamine-leads to feelings of euphoria, psychosis, delusions and extreme aggressiveness.
50Ecstasy:- a stimulant and hallucinogen-affects neurons in the brain by causing an over-production of serotonin.-creates shorter feelings of pleasure, however use can result in brain damage, and cardiac arrest.
51The venom of the black widow spider is called “latrotoxin” The venom of the black widow spider is called “latrotoxin”. This toxin results in a massive release of the neurotransmitter acetylcholine from the neuromuscular junctions of victims and may cause muscle spasms, pain, increased blood pressure, nausea and vomiting.
52Diseases of the Nervous System Parkinson’s Disease: wide-eyed, unblinking expression, involuntary tremor, muscle rigidity, shuffling gait. Ex. Muhammad Ali-dopamine deficiency caused by the degeneration of dopamine producing cells in the brain-
53-caffeine may offer protection against Parkinson’s disease as it prevents loss of dopamine
54Alzheimer’s Disease: characterized by loss of memory, senility, deterioration of cells in the basal nuclei, presence of tangles and plaques-possibly due to a malfunction of acetylcholine- seems to be linked to a gene located on chromosome #21
55Schizophrenia: delusions, random thoughts, disjointed thoughts, sensory hallucinations - may be the result of excessive activity of brain neurotransmitters such as dopamine
56Huntington’s Disease: progressive deterioration of the nervous system that leads to writhing movements, insanity and eventually death- seems to be caused by the malfunction of the inhibitory neurotransmitter GABA
57Depression: low affect, feeling blue, lack of or excessive sleep and eating patterns - seems to be linked to malfunctions in dopamine and seratonin, perhaps caused by an excess of monoamine oxidase enzymes
58Stroke: caused by interruption of blood flow to the brain which causes brain cells to perish.
59Epilepsy: is a seizure disorder where there is a sudden, un-explained surge of electrical activity through the brain with no specific known cause.Epilepsy.com
60Chemical Warfare1) Nerve Gas: inhibit acetylcholinesterase (enzyme that removed acetylcholine from the synaptic gap). Causes spastic paralysis which is continues muscle spasms2) Strychnine: similar to nerve gas, causes convulsions and spastic paralysis
61Central Nervous System (CNS) Is primarily responsible for the processing and organization of information.The CNS consists of two major structures:1. The Brain2. The Spinal Cord
62Spinal CordMade of 31 segmentsProtected by the vertebrae
64Spinal CordDorsal Root Ganglion – entry of sensory neurons to spinal cord and CNS, ganglion is the collection of cell bodiesVentral Root – exit of motor neurons from the spinal cord
65Meninges – 3 protective membranes surrounding the spinal cord and brain (dura mater, arachnoid, pia mater)Meningitis is an infection of the meninges (A spinal tap is a needle that is inserted between 2 vertebrates into the meninges to check for meningitis)
66Cerebrospinal Fluid – circulates between the inner and middle membranes of the brain and spinal cord.Provides protection, nutrient / waste exchange, etc.
70Hindbrain - The Unconscious Brain – important for autonomic functions required for survivalCerebellum – responsible for muscle co-ordination, posture, coordinated muscle movement and balance
71Medulla oblongata – controls heartbeat, respiration, blood pressure, reflex center for vomiting, sneezing, hiccupping, coughing and swallowingPons – connects the cerebrum to other parts of the brain, regulates breathing rate
73Midbrain – reflex center for head movements in response to visual stimuli, connects cerebrum to other parts of the brain
74Forebrain – responsible for conscious and unconscious actions Thalamus – central relay station- directs incoming sensory information to the cerebrum
75Hypothalamus – contains cells that produce some hormones, controls thirst, hunger, and controls many of the pituitary hormonesAlso aids in sleep regulation, sexual arousal, emotions (anger, fear, pain, pleasure)
76Cerebrum – largest part of the brain (80% of brain mass), left and right hemispheres. responsible for intellect, memory, consciousness and language.
77Lobes of the Cerebral Cortex Frontal Lobe –voluntary motor muscle movement, higher intellectual processes, personality/behavior, language
81Other parts of the brain Limbic System –emotions, associated with hypothalamus
82Pituitary Gland- Master Gland attaches to hypothalamus
83Corpus CallosumBundle of nerves that connects the two halves of the brainallows for integrated thoughts and coordinated responses
84Left brain – verbal, linguistic dominant Right brain – spatial, artistic, visual dominant
85Radioactive chemicals are injected into the bloodstream PET – Positron Emission TomographyRadioactive chemicals are injected into the bloodstreamdata is used to produce 2D or 3D images of the distribution of the chemicals throughout the brain and body.
86SPECT-Single Photon Emission Computed Tomography radioactive tracers and a scanner record datacomputer constructs 2D or 3D images of the active brain regions.
87MRI-Magnetic Resonance Imaging - magnetic fields and radio waves produce high-quality 2D or 3D images of brain structures without injecting radioactive tracers.
88EEG-Electroencephalography - electrodes placed on the scalp detect and measure patterns of electrical activity from the brain.
89CT-Computed Tomography Scan - a series of X-ray beams passed through the head.-images are then developed on sensitive film.-creates cross-sectional images of the brain
90Peripheral Nervous System (PNS) Cranial nerves – 12 pairs of sensory, motor and mixed nerves that control the face, neck and shouldersSpinal Nerves – 31 pairs of nerves that emerge from the spinal cord by two roots (one pair for each segment)
91Dorsal root nerves – contain sensory neurons and ganglia Ventral root nerves – contain motor neuronsAll other nerves not part of the CNS
93The PNS is subdivided into two major parts: The Somatic Nervous System-contains all the nerves that serve the muscular-skeletal system and the sensory organs.-conscious and deliberate.
94-non-voluntary actions The Autonomic Nervous System-non-voluntary actions-contains all the nerves that serve the internal organs.-unconscious and automatic.-made of two parts:
95Sympathetic nervous system -responsible for the 4 Fs: fight, flight, fright, or having sex response-ex) dilation of the pupils, increased heart rate, increased breathing rate, slowed digestion, enhanced performance, increase in blood sugar
96- brings the body back to normal levels Parasympathetic nervous system – responsible for the relaxation response (after fight, flight, fright, having sex)- brings the body back to normal levels