Essential knowledge 3.E.2:

1. Essential knowledge 3.E.2: Animals have nervous systems that detect external and internal signals, transmit and integrate information, and produce responses.

2. Nervous systems • Effector cells~ muscle or gland cells • Nerves~ bundles of neurons wrapped in connective tissue • Central nervous system (CNS)~ brain and spinal cord • Peripheral nervous system (PNS)~ sensory and motor neurons

3. Action potentials propagate impulses along neurons. • Evidence of student learning is a demonstrated understanding of each of the following: • 1. Membranes of neurons are polarized by the establishment of electrical potentials across the membranes. • 2. In response to a stimulus, Na+ and K+ gated channels sequentially open and cause the membrane to become locally depolarized. • 3. Na+/K+ pumps, powered by ATP, work to maintain membrane potential. • c. Transmission of information between neurons occurs across synapses. • Evidence of student learning is a demonstrated understanding of each of the following: • 1. In most animals, transmission across synapses involves chemical messengers called neurotransmitters. • To foster student understanding of this concept, instructors can choose an illustrative example such as: • • Acetylcholine • • Epinephrine • • Norepinephrine • • Dopamine • • Serotonin • • GABA • 2. Transmission of information along neurons and synapses results in a response. • 3. The response can be stimulatory or inhibitory. • d. Different regions of the vertebrate brain have different functions. • To foster student understanding of this concept, instructors can choose an illustrative example such as: • • Vision • • Hearing • • Muscle movement • • Abstract thought and emotions • • Neuro-hormone productio • • Forebrain (cerebrum), midbrain (brainstem) and hindbrain • (cerebellum) • • Right and left cerebral hemispheres in humans

4. The structure of the neuron allows for the detection, generation, transmission and integration of signal information. • Neuron~ structural and functional unit • Cell body~ nucleus and organelles • Dendrites~ impulses from tips to neuron • Axons~ impulses toward tips • Myelin sheath~ supporting, insulating layer • Schwann cells~ , which form the myelin sheath, are separated by gaps of unsheathed axon over which the impulse travels as the signal propagates along the neuron.

5. Simple Nerve Circuit • Sensory neuron: convey information to spinal cord • Interneurons: information integration • Motor neurons: convey signals to effector cell (muscle or gland) • Reflex: simple response; sensory to motor neurons • Ganglion (ganglia): cluster of nerve cell bodies in the PNS • Supporting cells/glia: nonconductiong cell that provides support, insulation, and protection

6. Neural signaling, I • Membrane potential (voltage differences across the plasma membrane) • Intracellular/extracellular ionic concentration difference • K+ diffuses out (Na+ in); large anions cannot follow….selective permeability of the plasma membrane • Net negative charge of about -70mV

7. Neural signaling, II • Excitable cells~ cells that can change membrane potentials (neurons, muscle) • Resting potential~ the unexcited state of excitable cells • Gated ion channels (open/close response to stimuli): photoreceptors; vibrations in air (sound receptors); chemical (neurotransmitters) & voltage (membrane potential changes) • Graded Potentials (depend on strength of stimulus): • 1- Hyperpolarization (outflow of K+); increase in electrical gradient; cell becomes more negative • 2- Depolarization (inflow of Na+); reduction in electrical gradient; cell becomes less negative

8. The Resting Potential

9. Neural signaling, III • Threshold potential: if stimulus reaches a certain voltage (-50 to -55 mV)…. • The action potential is triggered…. • Voltage-gated ion channels (Na+; K+) • 1-Resting state •both channels closed • 2-Threshold •a stimulus opens some Na+ channels • 3-Depolarization•action potential generated •Na+ channels open; cell becomes positive (K+ channels closed) • 4-Repolarization•Na+ channels close, K+ channels open; K+ leaves •cell becomes negative • 5-Undershoot•both gates close, but K+ channel is slow; resting state restored • Refractory period~ insensitive to depolarization due to closing of Na+ gates

10. The Action Potential

11. Neural signaling, IV • “Travel” of the action potential is self-propagating • Regeneration of “new” action potentials only after refractory period • Forward direction only • Action potential speed: • 1-Axon diameter (larger = faster; 100m/sec) • 2-Nodes of Ranvier (concentration of ion channels); saltatory conduction; 150m/sec

12. Synaptic communication • Presynaptic cell: transmitting cell • Postsynaptic cell: receiving cell • Synaptic cleft: separation gap • Synaptic vesicles: neurotransmitter releasers • Ca+ influx: caused by action potential; vesicles fuse with presynaptic membrane and release…. • Neurotransmitter

13. Signal transmission

14. Neurotransmitters • Acetylcholine (most common) •skeletal muscle • Biogenic amines(derived from amino acids) •norepinephrine •dopamine •serotonin • Amino acids • Neuropeptides(short chains of amino acids) •endorphin

15. Vertebrate PNS • Cranial nerves (brain origin) • Spinal nerves (spine origin) • Sensory division • Motor division •somatic system voluntary, conscious control •autonomic system √parasympathetic conservation of energy √sympathetic increase energy consumption

16. The Vertebrate Brain • Forebrain•cerebrum~memory, learning, emotion •cerebral cortex~sensory and motor nerve cell bodies •corpus callosum~connects left and right hemispheres•thalamus; hypothalamus • Midbrain •inferior (auditory) and superior (visual) colliculi • Hindbrain •cerebellum~coordination of movement•medulla oblongata/ pons~autonomic, homeostatic functions