Diploma Prep Nervous System PDF

Nervous and Endocrine Systems Nervous and Endocrine System Breakdown Nervous System (~10 marks) Endocrine System (~6-7 marks) 5 marks, 1NR - Glands & hormones (2) - Neuron (2) - Specific hormone functions - Impulse (1) (2)...

Nervous and Endocrine Systems Nervous and Endocrine System Breakdown Nervous System (~10 marks) Endocrine System (~6-7 marks) 5 marks, 1NR - Glands & hormones (2) - Neuron (2) - Specific hormone functions - Impulse (1) (2) - Synaptic transmission (2) - Negative feedback loops (ie 5 marks, 1NR TSH, ACTH) (1) - Brain (2) - What if (1) - Eye & Ear (2-3) - Disorder (1) Remember: Nervous System → speedy responses through nerve impulses Endocrine System → slower, long term responses through hormones Nervous System Myelination - Myelinated neurons: “white matter” of brain responsible for conducting nerve impulses - Can regenerate after injury - Unmyelinated neurons: “grey matter” of brain, responsible for processing information and generating nerve impulses - Can not regenerate after injury 3 Types of Neurons: work together in reflex arc Receptor R S I M E Effector Example 2 1 5 4 4 Stages of an Action Potential 1. Polarized/resting state 2. Depolarization 3. Repolarization 4. Refractory Period Action Potential K f s in + low flow s ou Na + t 2 1 2 7 0 4 0  Signal Transduction across a synapse = chemical event - Signal must travel across a synapse (space between axon terminal of one neuron to dendrites of another)  Neurotransmitters = chemical messengers - Released from presynaptic cell - Stored in synaptic vesicles in axon terminals - Diffuse across synaptic cleft and bind to receptors on the postsynaptic neuron (dendrites) - 2 types: - Excitatory - Inhibitory  Excitatory Neurotransmitters - Depolarize membranes by increasing Na+ permeability - Membrane potential moved towards threshold (becomes more positive) - Eg. acetylcholine = neurotransmitter in muscle cells causing contraction in muscle fiber cells - Cholinesterase required to break down acetylcholine after action potential Excitatory Neurotransmitters: Summation - multiple neurons fire releasing enough neurotransmitter to cause depolarization of postsynaptic membrane Inhibitory Neurotransmitters - Hyperpolarizes membranes by increasing permeability to K+ or Cl- - Membrane potential moved away from threshold (becomes more negative) - Eg. GABA: inhibits motor behaviour Excitatory vs Inhibitory Neurotransmitters Steps of Neurotransmitter Release 1. Action potential reaches axon terminal 2. Ca2+ channels within axon terminal open Ca2+ flows into the cell triggering movement of neurotransmitter vesicles towards the presynaptic membrane 3. Vesicles fuse to axon terminal membrane 4. Neurotransmitters are released and diffuse across synaptic cleft to post-synaptic membrane 5. Neurotransmitters reach postsynaptic membrane and bind to receptors 6. Binding of neurotransmitters to receptors triggers action potential in the corresponding cell 7. Neurotransmitters are released from the receptors and return to presynaptic neuron or are broken down by enzymes Common Neurotransmitters: Neurotransmitter Action Secretion Sites Major Effects Excitatory to skeletal muscles; Neuromuscular Skeletal muscle acetylcholine excitatory OR inhibitory at other regions, CNS, contraction locations PNS norepinephrine Excitatory or inhibitory CNS, PNS Wakefulness dopamine Generally excitatory CNS, PNS Voluntary movement and emotion serotonin Generally inhibitory CNS Sleep GABA Inhibitory CNS Motor behaviour 1243 Organization of the Nervous System Without thinking. Ie Think about doing heartbeat, digestion ut! ut! e ako illo F r Ch  ? MO Temp - cerebrum cerebellum occ. 2 4 1 5 CNS: The Spinal Cord - Links communication between the brain and peripheral nervous system - Sensory neurons within dorsal root carry info to spinal cord, motor neurons in ventral root relay info to effectors - Protected by cerebrospinal fluid and vertebrae 423 1 RSIME!  Types of Sensory Receptors Photoreceptors Stimulated by light (eg. rods & cones in the retina) Chemoreceptors Stimulated by chemicals (eg. taste buds on the tongue, olfactory receptors in the nose) Mechanoreceptors Stimulated by pressure (eg. hair cells of the inner ear) Thermoreceptors Stimulated by heat/cold (eg. nerve endings in the skin) The Eye  Photoreception - Vision is associated with stimulation of photoreceptors - Rods (light sensors) and cones (colour sensors) in the retina convert light energy into electrochemical impulses which the brain uses to form an image - Ciliary muscles change the shape of the lens to focus light into the retina Rods vs. Cones - Both found in the retina - Rods = respond to low-intensity light and detect black and white - Contain rhodopsin (light-sensitive pigment in the form of vitamin A) - vitamin A deficiency can result in “night blindness” - Cones = respond to high-intensity light to identify colour 2 1 4 3  (Contains basilar membrane) (Pina) Pathway of sound: Outer & Middle Ear - Pinna directs sound waves to the auditory canal where they hit the tympanum (eardrum), generating vibrations in the middle ear - Vibrations from sound waves hitting the tympanum are passed on and amplified by 3 ossicles (malleus, incus and stapes) - Vibrations on the oval window causes pressure changes in the inner ear Pathway of Sound: Inner Ear - Pressure changes stimulate movement of hair cells (organ of Corti) within the cochlea, generating an action potential in the auditory nerve - Action potential carries to temporal lobe where sound is interpreted Balance: Inner Ear - Pressure changes cause waves in the fluid of the semicircular canals (maintain dynamic equilibrium) - Fluid leaks/volume increase or failure of canals to flex properly in response to head change can result in balance disorders and/or vertigo 3 2 5 6