Synapses Information transmission occurs Narrow gap between a synaptic terminal of an axon and a signal receiving portion of a cell body Diffusion Electrical synapses –Gap junctions –Allow electric currents to flow directly from cell to cell Chemical synapses –Synaptic vesicles

IB wants you to know –Active potential reaches the terminal point of the pres synaptic neuron. –Depolarization through the use of Ca 2+ –Increased concentration of calcium ions causes the vesicles to fuse with the terminal membrane –Neurotransmitter released by exocytosis –Neurotransmitter diffuses across the synaptic cleft –Na + causes depolarization of post-synaptic membrane –Continues further as an action potential –Neurotransmitter is broken down to stop continuous synaptic transmission

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Direct Synaptic Transmission Ligand-gated ion channels –Can bind to the neurotransmitter Opens up the channel –Specific ions can enter = a postsynaptic potential Excitatory Postsynaptic Potentials (EPSP) –Depolarized (toward threshold) Inhibitory Postsynaptic Potentials (IPSP) –Hyperpolarized (away from threshold)

Postsynaptic Potentials Are graded Factors –# of neurotransmitters released –Get smaller with distance from synapses Temporal summation –EPSPs in rapid succession by the same synapses Spatial summation –EPSPs simultaneously by different synapses on the same postsynaptic neuron

Indirect Synaptic Transmission Neurotransmitter attaches onto a receptor (not part of the channel) Postsynaptic potentials are slower but last longer Uses a variety of pathways as a second messenger in the postsynaptic cell –Cyclic AMP (cAMP)

Neurotransmitters Chemical messengers that allows for information to be passed Some have more than a dozen receptors capable of producing various effects in postsynaptic cells –Acetylcholine (most common) –Biogenic Amines –Amino Acids –Gases

The vertebrate nervous system The central nervous system = brain + spinal cord The peripheral nervous system= Cranial nerves+ spinal nerves + ganglia (clusters of neurons) PNS transmits info to the CNS –Movement –Internal environment

Continued Mammals have 12 pairs of cranial nerves (organs in the head and upper body) and 31 pairs of spinal nerves PNS can be divided into –Somatic nervous system To and from skeletal muscles (external stimuli, conscious control) –Autonomic nervous system Regulates internal environment (smooth and cardiac muscles, INVOLUNTARY) –3 divisions Sympathetic, Parasympathetic, Enteric

Continued Sympathetic division- FIGHT OR FLIGHT, arousal, generating energy Parasympathetic division- CALM, decrease in heart rate Enteric division- neurons in the digestive tract (control secretion) (can be independent but usually regulated by the other two)

Brain Development 3 parts in embryo –Forebrain –Midbrain –Hindbrain Divided both structurally and functionally –5 parts in 5 weeks of embryo development –Forebrain = Telencephalon, Diencephalon –Midbrain= Mesencephalon –Hindbrain= Encephalon, Myelencephalon Forebrain => Telencephalon => Cerebrum Cerebral cortex- outer portion of cerebrum

Brainstem Lower brain 3 parts –Medulla oblongata= breathing, heart activity, swallowing –The pons= helps medulla –The midbrain= centers for sensory info Homeostasis, coordination (movement), give information to higher brain centers Reticular formation- controls arousal and sleep, found within the core of the brainstem

Cerebellum Diencephalon Develops from the metencephalon Coordination during motor, perceptual functions Receives input for motor commands by the cerbrum 3 regions –Epithalamus (produce cerebrospinal fluid from blood) –Thalamus (input for sensory info going to cerebrum) + (output info motor info leaving cerebrum) –Hypothalamus (homeostasis) (thermostat, level of hunger thirst, other survival mechanisms)

Cerebrum Divided into right and left cerebral hemispheres Gray matter and white matter Basal nuclei – located deep inside the white matter (movement sequences) –Damage here can render a person immobile or incapable of learning movement sequences Neocortex- 6 layers of neurons on brains surface (very convoluted = high surface area low volume) Corpus callosum – communication between the left and right cerebral cortices