Chapter 14

 

Chapter 14: Brain Structure and Function

 

14.1 Nervous System Tissues

  • The _____________________________ receives and interprets messages about what the body is doing and feeling and decides how to respond
    • 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

 

  • 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 _________________________________
  • The general senses are:
    • Temperature
    • Pain
    • Touch
    • Pressure
    • Proprioception (body position)
  • The special senses are smell, taste, equilibrium, hearing and vision

 

  • 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

 

  • 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
  • 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 _________________________

 

  • 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

 

  • 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

 

  • 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

 

  • 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
  • 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

 

  • 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

 

  • 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

 

  • 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

 

  • 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

 

  • 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
  • _____________________________ 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

 

  • 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

 

  • 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

 

  • The _________________________________________ dominates when there aren’t many messages from external receptors
    • Energy is used to maintain basics such as digestion and thermoregulation
  • 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