PowerLecture: Chapter 34 Integration and Control: Nervous System

Fig. 34-1, p.572

p.573a

Nerve Net  interconnected nerve cells that can send impulses 2 directions Figure 34.3 Page 574

Bilateral Nervous Systems FlatwormEarthworm CrayfishGrasshopper Fig a Page 589

Fig. 34-4, p.575

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

Neurons  3 classes Sensory neurons Interneurons Motor neurons

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

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

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

Resting Potential  -70millivolts Charge difference across membrane of neuron  inside cell negative

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

outside plasma membrane inside K+K+ K+K+ Na + p.577

How Ions Move across Membrane 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 Interstitial fluid Plasma membrane Cytoplasm Na + leaks in Na + pumped in Na + pumped out Na + leaks out K + leaks out Figure 34.7 Page 577

Action Potential  Temporary reversal in membrane potential  Voltage change causes voltage-gated channels to open  Inside neuron becomes more positive than outside

Action Potential Na + K+K+ K+K+ K+K+ K+K+ K+K+ K+K+ K+K Figure 34.8a-d Page

Positive Feedback 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 same size  Stimulation below threshold level, no action potential  Above threshold level, always same size

Repolarization  Movement of Na + out repolarizes cell  back to resting potential

one of a pair of stellar nerves with giant axons inside Fig. 34-9a, p.579

electrode outside electrode inside unstimulated axon Fig. 34-9b, p.579

Fig. 34-9c,d, p.579

stimulated axon Fig. 34-9e1, p.579

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

Propagation of Action Potentials  Action potential in one part of axon triggers neighboring region  Action potential travels as a wave of depolarization along cell

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 presynaptic cell plasma membrane of postsynaptic cell synaptic cleft membrane receptor Figure 34.10a Page 580

Synaptic Transmission  Action potential in axon ending of presynaptic cell causes voltage-gated calcium channels to open  calcium Flow into presynaptic cell releases 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 postsynaptic cell

Ion Gates Open ions neurotransmitter receptor for neurotransmitter gated channel protein Figure 34.10c Page 580

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

Fig b,c, p.582

Neuropeptides  Neuromodulators – magnify or reduce the effects of neurotransmitters substance P substance P enkephalins enkephalins endorphins endorphins

Neuroglia  more than half the volume of vertebrate nervous system  metabolically assist, structurally support, and protect the neurons

Fig , p.583

Nerve  Bundle of axons within connective tissue sheath Figure Page 584 axon myelin sheath nerve fascicle

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

Multiple Sclerosis  Nerve fibers lose their myelin  Slows conduction  Symptoms include visual problems, numbness, muscle weakness, and fatigue

Reflexes  Automatic movements in response to stimuli  Most reflexes involve an interneuron  Reflex arcs - sensory neurons synapse directly on motor neurons

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

Central and Peripheral Nervous Systems  Central nervous system (CNS) Brain Brain Spinal cord Spinal cord  Peripheral nervous system Nerves that thread through the body Nerves that thread through the body

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  Originate in Ganglia near the thoracic and lumbar regions of the spinal cord  Promote fight-or-flight response

Parasympathetic Nerves  Originate in the brain and the sacral region of the spinal cord  Promote housekeeping responses such as digestion

Dr. Robert Sapolsky (Stanford Neurobiologist) studies long term health effects of stress

Function of the Spinal Cord  signals between brain and peripheral nerves  direct reflex connections in the spinal cord  Spinal reflexes do not involve brain

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

Development of the Brain  develops from a hollow neural tube  Forebrain, midbrain, and hindbrain form

Functional Regions  Expansion and modification of dorsal nerve cord produced functionally distinct regions FOREBRAIN MIDBRAIN HINDBRAIN (start of spinal cord) Figure 34.19a Page 588

Brain Regions Hindbrain (Rhombencephalon) Medulla oblongata - controls autonomic Medulla oblongata - controls autonomic functions functions Cerebellum - controls motor skills and Cerebellum - controls motor skills and posture posture Pons - controls signals between cerebellum Pons - controls signals between cerebellum and forebrain and forebrain

Brain Regions Midbrain ( Mesencephalon) Tectum - Visual Processing Tectum - Visual Processing

Brain Regions Forebrain (Prosencephalon) Cerebrum - Higher thinking skills Cerebrum - Higher thinking skills Thalamus - sorting sensory input Thalamus - sorting sensory input Hypothalamus - Homeostatic control Hypothalamus - Homeostatic control

forebrain midbrain hindbrain Brain at 7 weeks Fig b, p.588 Brain Development

Brain at 9 weeks Fig c, p.588 Brain Development

Brain at birth Fig d, p.588 Brain Development

Divisions of Brain DivisionMain Parts Forebrain Midbrain Hindbrain Cerebrum Olfactory lobes Thalamus Hypothalamus Limbic system Pituitary gland Pineal gland Tectum Pons Cerebellum Medulla oblongata anterior end of the spiral cord Figure 34.19a Page 588

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

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

Reticular Formation  Interneuron Mesh extends from spinal cord, through brain stem, into cerebral cortex

Anatomy of the Cerebrum  Largest and most complex part of human brain  cortex highly folded  divided into left and right hemispheres

Lobes of the Cerebrum Temporal Frontal Parietal Occipital Primary motor cortex Primary somatosensory cortex Figure Page 590

Fig , p.590

Limbic System  Controls emotions - 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

Sperry’s Split Brain Expts.  Corpus collosum severed  No communication between hemispheres cowboy

Memory  Stored in stages Temporary Temporary Short-term memory Short-term memory Long-term memory Long-term memory

Sensor stimuli, as from the nose, eyes, and ears Temporal storage in cerebral cortex SHORT-TERM MEMORY Recall of stored input LONG-TERM MEMORY Input forgotten Input irretrievable Emotional state, having time to repeat (or rehearse) input, and associating the input with stored categories of memory influence transfer to long-term storage Fig , p.593

premotor cortex motor cortex for this example, a visual stimulus Fig a, p.593 corpus striatum caudate nucleus lentiform nucleus Memory Circuitry

Drugs and Addiction  A drug is a substance introduced into the body to provoke a specific physiological response  In addiction, a drug assumes an “essential” biochemical role in the body

Addiction

Stimulants  Increase alertness and body activity, then cause depression Caffeine Caffeine Nicotine - mimics acetylcholine Nicotine - mimics acetylcholine Cocaine - blocks neurotransmitters reuptake Cocaine - blocks neurotransmitters reuptake Amphetamines & Ecstasy - induce dopamine release Amphetamines & Ecstasy - induce dopamine release

Fig a, p.595 PET Scan  Cocaine’s long term effect

Fig b, p.595

Depressants  Lower activity of nerves and parts of the brain Barbiturates Barbiturates Alcohol - acts directly on the plasma membrane to alter cell function Alcohol - acts directly on the plasma membrane to alter cell function

Hallucinogens and Marijuana  Skew sensory perception by interfering with action of neurotransmitters  LSD affects action of serotonin  Marijuana is a depressant at low dose; it can also cause disorientation, anxiety, delusion, and hallucinations

Teen Brain  Prefrontal cortex still developing  Amygdala in growth spurt  Increased need for sleep

Synaptic Integration Membrane potential (milliseconds) EPSP IPSP what action potential spiking would look like threshold resting membrane potential integrated potential Figure Page 581