Neural Control Chapter 33 Part 2
33.6 A Smorgasbord of Signals Different types of neurons release different neurotransmitters; Parkinson s disease involves dopamine-secreting neurons and motor control
Fig. 33-13a, p. 562
Fig. 33-13b, p. 562
Fig. 33-13c, p. 562
Major Neurotransmitters and Their Effects
The Neuropeptides Neuromodulators Neuropeptides made by some neurons that influence the effects of neurotransmitters Substance P enhances pain Enkephalins and endorphins are pain killers
33.7 Drugs Disrupts Signaling Psychoactive drugs exert their effects by interfering with the action of neurotransmitters Stimulants (nicotine, caffeine, cocaine, amphetamines) Depressants (alcohol, barbiturates) Analgesics (narcotics, ketamine, PCP) Hallucinogens (LSD, THC)
PET Scan: Effects of Cocaine
Signs of Drug Addiction
33.2-33.7 Key Concepts How Neurons Work Messages flow along a neuron s plasma membrane, from input to output zones Chemicals released at a neuron s output zone may stimulate or inhibit activity in an adjacent cell Psychoactive drugs interfere with the information flow between cells
33.8 The Peripheral Nervous System Peripheral nerves carry information to and from the central nervous system Nerves are bundled axons of many neurons Each axon is wrapped in a myelin sheath that increases transmission speed
Nerve Structure and Function
Nerve Structure and Function
Nerve Structure and Function
Nerve Structure and Function
myelin sheath axon blood vessels nerve fascicle (a number of axons bundled inside connective tissue) the nerve s outer wrapping Fig. 33-15a, p. 564
unsheathed node axon b Jellyrolled Schwann cells of an axon s myelin sheath Fig. 33-15b, p. 564
Na + action potential resting potential resting potential Fig. 33-15c, p. 564
K + Na + resting potential restored action potential resting potential Fig. 33-15d, p. 564
Animation: Nerve structure
Animation: Ion flow in myelinated axons
Divisions of the Peripheral Nervous System Somatic nervous system Conducts information about the environment to the central nervous system (involuntary) Controls skeletal muscles (voluntary) Autonomic nervous system Conducts signals to and from internal organs and glands
Divisions of the Autonomic Nervous System The two divisions of the autonomic nervous system have opposing effects on effectors Sympathetic neurons are most active in times of stress or danger (fight-flight response) Parasympathetic neurons are most active in times of relaxation
Divisions of the Autonomic Nervous System
eyes salivary glands optic nerve midbrain medulla oblongata heart larynx bronchi lungs vagus nerve cervical nerves (8 pairs) stomach liver spleen pancreas kidneys adrenal glands thoracic nerves (12 pairs) (most ganglia near spinal cord) small intestine upper colon lower colon rectum bladder uterus genitals (all ganglia in walls of organs) pelvic nerve lumbar nerves (5 pairs) sacral nerves (5 pairs) Fig. 33-16, p. 565
Animation: Autonomic nerves
33.9 The Spinal Cord Spinal cord Runs through the vertebral column and connects peripheral nerves with the brain Serves as a reflex center Central nervous system (CNS) The brain and spinal cord
Protective Features Meninges Three membranes that cover and protect the CNS Cerebrospinal fluid Fills central canal and spaces between meninges Cushions blows
White Matter and Gray Matter White matter Bundles of myelin-sheathed axons (tracts) Outermost portion of spinal cord Gray matter Nonmyelinated structures (cell bodies, dendrites, neuroglial cells)
Reflex Pathways Reflex An automatic response to a stimulus Stretch reflex, knee-jerk reflex, withdrawal reflex Spinal reflexes do not involve the brain Signals from sensory neurons enter the cord through the dorsal root of spinal nerves Commands for responses go out on the ventral root of spinal nerves
Stretch Reflex
STIMULUS Biceps stretches. A Fruit being loaded into a bowl puts weight on an arm muscle and stretches it. Will the bowl drop? NO! Muscle spindles in the muscle s sheath also are stretched. muscle spindle neuromuscular junction B Stretching stimulates sensory receptor endings in this muscle spindle. Action potentials are propagated toward spinal cord. E Axon terminals of the motor neuron synapse with muscle fibers in the stretched muscle. F ACh released from the motor neuron s axon terminals stimulates muscle fibers. G Stimulation makes the stretched muscle contract. Ongoing stimulations and contractions hold the bowl steady. D The stimulation is strong enough to generate action potentials that selfpropagate along the motor neuron s axon. C In the spinal cord, axon terminals of the sensory neuron release a neurotransmitter that diffuses across a synaptic cleft and stimulates a motor neuron. RESPONSE Biceps contracts. Fig. 33-18, p. 567
Animation: Stretch reflex
33.8-33.9 Key Concepts Vertebrate Nervous System The central nervous system consists of the brain and spinal cord The peripheral nervous system includes many pairs of nerves that connect the brain and spinal cord to the rest of the body The spinal cord and peripheral nerves interact in spinal reflexes
33.10 The Vertebrate Brain The brain is the body s main information integrating organ, part of the CNS During development, the brain is organized as three functional regions: forebrain, midbrain and hindbrain
Hindbrain and Midbrain The hindbrain includes the medulla oblongata, the pons, and the cerebellum The midbrain in mammals is reduced The brain stem (pons, medulla, and midbrain) is involved in reflex behaviors
The Forebrain Cerebrum Main processing center in humans Evolved as an expansion of the olfactory lobe Thalamus and hypothalamus Important in thirst, temperature regulation, and other responses related to homeostasis
Development of the Human Brain
Fig. 33-19 (a-c), p. 568
forebrain midbrain hindbrain Fig. 33-19 (a-c), p. 568
Protection at the Blood-Brain Barrier Blood-brain barrier Protects the CNS from harmful substances Tight junctions form a seal between adjoining cells of capillary walls Some toxins (nicotine, alcohol, caffeine, mercury) are not blocked
The Human Brain Cerebellum Has more interneurons than other brain regions Involved in balance, motor skills and language Cerebrum Divided into two hemispheres, coordinated by signals across the corpus callosum Each hemisphere deals with the opposite side of the body
Major Brain Regions of Vertebrates
olfactory lobe forebrain midbrain hindbrain FISH AMPHIBIAN REPTILE BIRD shark frog alligator goose Fig. 33-20a, p. 569
Fig. 33-20b, p. 569
part of optic nerve corpus callosum hypothalamus thalamus pineal gland location midbrain cerebellum pons medulla oblongata Fig. 33-20b, p. 569
Animation: Sagittal view of a human brain
33.11 The Human Cerebrum Each cerebral hemisphere is divided into frontal, temporal, occipital and parietal lobes Cerebral cortex Outermost gray matter of the cerebrum Controls voluntary activity, sensory perception, abstract thought, language and speech Distinct areas receive and process signals
Lobes of the Brain
frontal lobe (planning of movements, aspects of memory, inhibition of unsuitable behaviors) primary motor cortex primary somatosen sory cortex parietal lobe (visceral sensations) Wernicke s area Broca s area temporal lobe (hearing, advanced visual processing) occipital lobe (vision) Fig. 33-21, p. 570
Animation: Receiving and integrating areas
Functions of the Cerebral Cortex Specific areas of the cerebral cortex correspond to specific body parts or functions Examples: The body is spatially mapped out in the primary motor cortex of each frontal lobe Association areas are scattered throughout the cortex, but not in motor or sensory areas
The Primary Motor Cortex
Association Areas Integrate Inputs
Motor cortex activity when speaking Prefrontal cortex activity when generating words Visual cortex activity when seeing written words Fig. 33-23, p. 570
Connections With the Limbic System The cerebral cortex oversees the limbic system Limbic system Governs emotions, assists in memory, correlates emotional-visceral responses Includes the hypothalamus, hippocampus, amygdala, and cingulate gyrus
Limbic System Components
(olfactory tract) cingulate gyrus thalamus hypothalamus amygdala hippocampus Fig. 33-24, p. 571
Making Memories The cerebral cortex receives information and processes some of it into memories Memory forms in stages Short-term memory lasts seconds to hours Long-term memory is stored permanently Skill memory involves the cerebellum Declarative memory stores facts and impressions
Stages in Memory Processing
Sensory stimuli, as from the nose, eyes, and ears Temporary storage in the cerebral cortex Input forgotten SHORT-TERM MEMORY Recall of stored input Emotional state, having time to repeat (or rehearse) input, and associating the input with stored categories of memory influence transfer to long-term storage LONG-TERM MEMORY Input irretrievable Fig. 33-25, p. 571
Sensory stimuli, as from the nose, eyes, and ears Temporary storage in the cerebral cortex Input forgotten SHORT-TERM MEMORY Recall of stored input Emotional state, having time to repeat (or rehearse) input, and associating the input with stored categories of memory influence transfer to long-term storage LONG-TERM MEMORY Input irretrievable Stepped Art Fig. 33-25, p. 571
33.12 The Split Brain Investigations by Roger Sperry into the importance of information flow between the cerebral hemispheres showed that the two halves of the brains have a division of labor Typically, math and language skills reside in the left hemisphere; the right hemisphere interprets music, spatial relationships, and visual inputs
Visual Information and the Brain
Left Half of Visual Field Right Half of Visual Field COWBOY COW BOY pupil optic nerves retina corpus callosum left visual cortex optic chiasm right visual cortex Fig. 33-26, p. 572
Animation: Path to visual cortex
Split-Brain Studies
33.13 Neuroglia The Neurons Support Staff Neuroglial cells make up the bulk of the brain The adult brain has four types of neuroglial cells Oligodendrocytes make myelin Microglia have immune system functions Astrocytes secrete various substances, take up neurotransmitters, assist in immune defenses, and stimulate formation of the blood-brain barrier Ependymal cells line brain cavities
Astrocytes
About Brain Tumors Unlike neurons, neuroglia continue to divide in adults, and can be a source of primary brain tumors (gliomas) Exposure to ionizing radiation such as x-rays, or to chemical carcinogens, increases risk
33.10-33.13 Key Concepts About the Brain The brain develops from the anterior part of the embryonic nerve cord A human brain includes evolutionarily ancient tissues and newer regions that provide the capacity for analytical thought and language Neuroglia make up the bulk of the brain
Animation: Action potential
Animation: Human brain development
Animation: Organization of the spinal cord
Animation: Primary motor cortex
Animation: Regions of the vertebrate brain
Animation: Structures involved in memory
Animation: Synapse function
Animation: Synaptic integration
ABC video: New Nerves
Video: In pursuit of ecstasy
Video: Brain stem
Video: Limbic system dissection