Fig. 34-1, p.572

Don’t Do Drugs read the intro to ch 34 p.573a

Fig. 34-2, p.574 stimulus receptors integrators motor neurons effectors response muscles, glands interneurons sensory neurons Line of Communication

Fig. 34-4, p.575

Peripheral Nervous System  Somatic nerves Motor functions Motor functions (Shown in green) (Shown in green)  Autonomic nerves Visceral functions Visceral functions (Shown in red) (Shown in red)

Two Types of Autonomic Nerves  Sympathetic  Parasympathetic  Most organs receive input from both  Usually have opposite effects on organ

Sympathetic Nerves  Promote responses that prepare the body for stress or physical activity (fight-or-flight response)

Parasympathetic Nerves  Promote housekeeping responses such as digestion

Both Systems Are Usually Active  Most organs are continually receiving both sympathetic and parasympathetic stimulation  For example, sympathetic nerves signal heart to speed up; parasympathetic stimulate it to slow down  Which dominates depends on situation

Communication Lines Stimulus (input) Receptors (sensory neurons) Integrators (interneurons) motor neurons Effectors (muscles, glands) Response (output) Figure 34.5 Page 575

Fig. 34-6d2, p.576 Neurons

Motor Neuron dendrites cell body Input Zone Trigger Zone Conducting Zone axon Output Zone axon endings Stepped Art Fig. 34-6d1, p.576

Neuron structure and function Neurons

Three Classes of Neurons  Sensory neurons  Interneurons  Motor neurons

cell body axon dendrites Fig. 34-6a, p.576

axon dendrites cell body Fig. 34-6b,c, p.576 dendrites

Fig. 34-6d1, p.576 dendrites cell body trigger zone input zone conducting zone output zone axon endings axon Structure of a Neuron

How Ions Move across Membrane resting potential video Passive transporters with open channels Passive transporters with voltage-sensitive gated channels Active transporters Lipid bilayer of neuron membrane Interstitial fluid CytoplasmNa + /K + pump Figure 34.7 Page 577

Pumping and Leaking (find the diagram error) Interstitial fluid Plasma membrane Cytoplasm Na + leaks in K + pumped in Na + pumped out Na + leaks out K + leaks out Figure 34.7 Page 577

Ion concentrations Ion Movement

Ion Concentrations at Resting Potential  Potassium (K + ) Higher inside axon Higher inside axon  Sodium (Na + ) Higher outside axon Higher outside axon

Action potential propagation Action Potential

Positive Feedback propagation neuron becomes more positive inside more gated channels for Na + open more Na + ions flow into the neuron

All or Nothing  All action potentials are the same size  If stimulation is below threshold level, no action potential occurs  If it is above threshold level, cell is always depolarized to the same level

Repolarization  Once peak depolarization is reached, Na + gates close and K + gates open  Movement of K + out of cell repolarizes the cell  The inside of the cell once again becomes more negative than the outside  Refractory period * unidirectional video 

Measuring membrane potential Membrane Potential

action potential threshold resting membrane potential Time (milliseconds) Membrane potential (millivolts) Figure 34.9f Page 579

Propagation of Action Potentials  An action potential in one part of an axon brings a neighboring region to threshold  Action potential occurs in one patch of membrane after another

Chemical Synapse  Gap between the terminal ending of an axon and the input zone of another cell synaptic vesicle plasma membrane of axon ending of presynapic cell plasma membrane of postsynapic cell synaptic cleft membrane receptor Figure 34.10a Page 580

Synaptic Transmission  Action potential at end of presynaptic cell axon causes voltage-gated calcium channels to open  Flow of calcium into presynaptic cell causes release of neurotransmitter into synaptic cleft

Synaptic Transmission  Neurotransmitter diffuses across cleft and binds to receptors on membrane of postsynaptic cell  Binding of neurotransmitter to receptors opens ion channels in the membrane of postsynaptic cell

Synapse function Synaptic Transmission

Chemical synapse Chemical Synapse

neuromuscular junction part of a skeletal muscle motor neuron axons from spinal cord to skeletal muscle cells transverse slice of spinal cord Fig a, p.581

muscle fiber axon ending Fig b, p.581

Neurotransmitters  ACh  Norepinephrine  Epinephrine  Dopamine  Serotonin  GABA  Derived from amino acids

Neuroglia cells  > half the volume of the nervous system  Cells that metabolically assist, structurally support, and protect the neurons

Types of Neuroglia  Oligodendrites make myelin in the brain  Schwann cells make myelin in peripheral nerves  Astrocytes - control ion & neurotrans conc.  - make lactate to fuel neurons  - make nerve growth factor

Nerve  A bundle of axons enclosed within a connective tissue sheath Figure Page 584 axon myelin sheath nerve fascicle

Myelin Sheath  A series of Schwann cells  Sheath blocks ion movements  Action potential must “jump” from node to node Figure 34.15b Page 584

Nerve structure Nerve

Ion Flow Ion flow in myelinated axons

Reflexes  Automatic movements made in response to stimuli  In the simplest reflex arcs, sensory neurons synapse directly on motor neurons  Most reflexes involve an interneuron

Stretch Reflex STIMULUS Biceps stretches. Response Biceps contracts. Figure Page 585 motor neuron sensory neuron

Stretch Reflex Stretch reflex

Function of the Spinal Cord  Expressway for signals between brain and peripheral nerves  Sensory and motor neurons make direct reflex connections in the spinal cord  Spinal reflexes do not involve the brain

Structure of the Spinal Cord spinal cord ganglion nerve vertebra meninges (protective coverings) Figure Page 587

Spinal Cord Organization of the spinal cord

Vertebrate Brains olfactory lobe (part of forebrain) forebrain midbrain hindbrain fish (shark) reptile (alligator) mammal (horse) forebrain midbrain hindbrain olfactory lobe Figure Page 589

Vertebrate Brains Regions of the vertebrate brain

Cerebrospinal Fluid  Surrounds the spinal cord  Fills ventricles within the brain  Blood-brain barrier controls which solutes enter the cerebrospinal fluid Figure Page 588

Anatomy of the Cerebrum  Largest and most complex part of human brain  Outer layer (cerebral cortex) is highly folded  A longitudinal fissure divides cerebrum into left and right hemispheres

Limbic System  Controls emotions and has role in memory (olfactory tract)cingulate gyrusthalamus amygdala hippocampus hypothalamus Figure Page 591

Motor cortex activity when speaking Prefrontal cortex activity when generating words Visual cortex activity when seeing written words Fig b, p.590

Sensory Pathway Path to visual cortex