Chapter 14: Brain Structure and Function
14.1 Nervous System Tissues
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The _____________________________ receives and interprets messages about what the body is doing and feeling and decides how to respond
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Two cell types are involved:
- ____________________________ carry electrical and chemical messages between the brain and other parts of the body
- ____________________________ support and nourish neurons, repair the brain after injury and attack invading bacteria
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Two cell types are involved:
- Signals travel along the length of neurons, pass through synapses, and ultimately move on to muscles and glands, which are the _______________________
- Effectors help the body respond to environmental changes
- Sensory input is detected by _________________________________
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The general senses are:
- Temperature
- Pain
- Touch
- Pressure
- Proprioception (body position)
- The special senses are smell, taste, equilibrium, hearing and vision
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The nervous system has two main divisions:
- The ________________________________________ is made up of the brain and spinal cord
- The ________________________________________ is the network of nerves radiating from the CNS throughout the body
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There are three general categories of neurons:
- ___________________________________ carry input toward the CNS
- ___________________________________ carry information away from the CNS
- ___________________________________ link sensory and motor neurons within the brain or spinal cord
- Many neurons are covered by a ________________________________
- Myelin acts to insulate neurons, prevent sideways message transmission, and thus increase transmission speed
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The myelin sheath of PNS neurons is formed by glial cells called _________________________ that wrap around the axons
- CNS myelinated neurons are called ________________________________, while non-myelinated CNS axons are called _______________________________
- Bundles of myelinated axons in the PNS are called _______________________
- When myelinated axons are bundled together in the CNS, they are called _________________________
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The myelin sheath has tiny unmyelinated gaped called __________________________
- Nerve impulses jump from one node of Ranvier to the next, greatly increasing signal speed (100x faster than unmyelinated neurons)
- Electrical changes (_________________________) along nerve cells carry information
- Many types of stimuli – touch, sound, light, taste, temperature, and smell – excite sensory neurons
- Sensory information is transmitted to the CNS, which responds through motor nerved to muscles and glands
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An ________________________________ is a difference in charge between two regions
- A resting axon has a net negative charge in the cytoplasm as opposed to the outside
- This is the ______________________________, resulting from ionic concentration differences
- Sodium ion (Na+) concentration is greater outside the axon than inside, and potassium ion (K+) concentration is greater inside the axon than outside
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The concentration difference is maintained by a membrane protein called the ____________________________________, which actively (requires energy) moves sodium out of the cell and potassium in
- Three sodium ions are moved out for every two potassium ions pumped in
- This puts more positive ions outside the membrane than inside
- An impulse requires a rapid change in membrane polarity
- An _________________________________ is a brief reversal of the axon’s membrane potential
- The action potential is propagated along the length of the axon if the change in membrane potential is above a certain threshold level (________________________________)
- The more intense the stimulus, the more often the axon fires
- The action potential declines as sodium channels close and potassium channels open, so the potassium can leave
- _____________________________ occurs when the potassium exits and the inside again becomes more negative than the outside
- When the action potential passes, the sodium-potassium pump restores the resting potential of the neuron
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Once the action potential has moved on, the affected region of the membrane undergoes a __________________________________
- The sodium gate close preventing another action potential
- At the end of an axon, the signal must pass to another axon or to a receptor across a ___________________________
- A synapse is made up of a terminal on the ________________________ neuron and the membrane on the __________________________ neuron
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Vesicles filled with _____________________________________ are located in the presynaptic space
- Each is filled with a specific neurotransmitter
- When an impulse reaches the terminal, the neurotransmitter is released into the synapse
- The neurotransmitter binds to specific receptors on the postsynaptic side of the synapse
- The neurotransmitter/receptor complex initiates a rapid influx of sodium on the postsynaptic side of the synapse, causing an action potential
- The nerve impulse travels from one neuron to the next until the signal reaches an effector
- Many axons can synapse with one neuron
14.2 The Central Nervous system
- Sense organs transmit information to the CNS
- The CNS processes the sensory information, and a response is sent out to the body
- CNS neurons tend to be highly specialized and they do not divide
- Damaged CNS neurons cannot be repaired, resulting in permanent impairment
- Spinal cord damage results in lifelong paralysis because messages from the CNS to muscled can’t be transmitted
- Brain injury is also often permanent
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The brain and spinal cord are the two components of the CNS
- Both are protected by bone and three layers of connective tissue, the ___________________
- __________________________________ surrounds and cushions the CNS structures and fills its cavities
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The ________________________ connects the brain and the CNS
- It is composed of fibers that control reflexes and transmit impulses to and from the brain
- The spinal cord is made mostly of interneurons
- In cross section, the spinal cord has white matter arranged around a butterfly shaped area of gray matter
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The brain is where sensory information is reached and where body activities are directed and coordinated
- The brain receives action potentials, integrates the signals, and generates a response
- Specialized areas in the brain integrate different types of information or perform specific motor tasks
- The brain is subdivided into several areas, including the cerebrum, thalamus, hypothalamus, cerebellum, and brain stem (midbrain, pons, medulla oblongata)
- The ______________________ controls language, memory, sensations, and decision making
- The cerebrum has two hemispheres, each divided into four lobes
- The wrinkled outer surface of the cerebrum is the ___________________________
- The cortex contains centers for making and understanding speech, areas for visual and other sensory input, and areas that allow planning
- A deep fissure divides the cerebrum into right and left hemispheres, which are connected by the _________________________
- The ________________________ and ______________________________ are located inside the brain in between the two cerebral hemispheres
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The thalamus relays input between the brain and spinal cord
- Pain, pressure, and temperature information is received by the thalamus, which integrates the signal and passes it to the cerebrum
- The cerebrum processes the input and sends appropriate signals to the spinal cord and muscles
- The hypothalamus is positioned just under the thalamus
- The hypothalamus controls sex drive, pain, pressure, hunger, thirst, blood pressure, and body temperature
- The hypothalamus also released hormones that regulate egg and sperm production, the menstrual cycle, and other physiological processes
- The ________________________ controls balance, muscle movement, and coordination
- Damage to the cerebellum results in rigidity, and in severe cases, jerky motion
- The cerebellum is located beneath the rear portion of the cerebral hemispheres
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The ___________________ is made up of the ____________________, _________________, and _____________________________ and lies below the thalamus and hypothalamus
- It governs heartbeat, respiration, swallowing, and coughing
- The midbrain, which adjusts sensitivity of eyes to light and ears to sound
- The pons allows messages to travel between brain and spinal cord
- The medulla oblongata conveys information between the spinal cord and other parts of the brain
- Together, the pons and medulla oblongata regulate breathing rate
- Brain functions are divided between the two cerebral hemispheres
- The __________________________________ tends to control the right side of the body, and vice versa
- The areas for speech, reading, and math are in the ________________________________
- Spatial perception and the centers for music and artistic creation are in the _________________________________
14.3 The Limbic System and Memory
- ________________________ involves storing information that can be retrieved sometime in the future
- Short term or working memory is memory that was stored within the past few hours
- Long term memory involves creating synapses to form pathways in the cerebral cortex that can be activated in the future
14.4 Peripheral Nervous System
- The ______________________________________ relays sensory and motor information between the CNS and the rest of the body
- The PNS has two kinds of nerves: cranial and spinal
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_____________________________ connect to the brain
- Cranial nerves tend to serve the head, neck, and face
- Some cranial nerves are only sensory, some only motor, and some are mixed nerved carrying both sensory and motor fibers
- _____________________________ connect to the spinal cord
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The PNS has two subdivisions: somatic and autonomic
- The ____________________________ controls skeletal muscles and helps the organism interact with its environment
- ________________________ are a component of the somatic system. They are automatic (involuntary) responses to stimuli
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The ________________________________________ innervates smooth and cardiac muscle, regulates cardiovascular activity, digestion, metabolism, and thermoregulation
- This system is not under conscious control
- It is divided into _________________________________ and _______________________________ divisions based on the brain and spinal cord regions from which the neurons originate
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The _________________________________________ dominates when there aren’t many messages from external receptors
- Energy is used to maintain basics such as digestion and thermoregulation
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The _____________________________________ dominates under conditions of excitement or danger
- Energy is used to get ready for a fight or flight; basic maintenance operations are put on hold