Chapter 7: Functional Organization of Nervous System

How many distinct layers does the mammalian cortex have?

6

If the central pattern generator for a human walking is located in the spinal cord, then is the brain required at all for successful walking behavior? Justify your answer.

A central pattern generator is a subset of neurons that can maintain spontaneous rhythmic output in the absence of sensory input. Therefore, the basic neural control for coordinating the action of the limbs during walking is housed in the spinal cord, and it can maintain its own activity without input from the brain. However, in a natural environment, inputs from the brain ARE required for a variety of other tasks associated with successful locomotion. For example, the cortex and brainstem are required to initiate locomotion. In other words, while the central pattern generator can maintain its own activity without input from the brain, it does, in fact, need a brain "trigger" in order to start. The cerebellum is required for balance and coordination to prevent the human from falling over. The brainstem controls the speed of locomotion. The cortex assists in regulating gait based on visual inputs such as obstacles and uneven terrain. Even though the central pattern generator can control basic muscular coordination, other sensory inputs and higher integrative inputs are required for successful walking behavior in a real setting

__________ is the evolutionary trend that describes the concentration of nervous tissue and sense organs at one end of the body.

Cephalization

Describe five differences between the actions of the parasympathetic and sympathetic nervous systems on the same effector organs. For example, the parasympathetic system causes urine release from the bladder, while the sympathetic system causes urine retention.

Effector organ Parasympathetic effect Sympathetic effect Pupil of eye Constricts Dilates Heart Slows heart rate Increases rate and force of contraction Arterioles None Constricts Digestive tract Increased motility and secretion Decreased motility and secretion Bladder Release of urine Retention of urine Sweat glands General sweating Localized sweating Bronchioles of lungs Constricts Dilates Adipose tissue None Fat breakdown

__________ neurons relay information from integrating centers such as the brain to effector organs like muscles or glands.

Efferent

What does the midbrain do in fish and amphibians?

It coordinates reflex responses to auditory and visual stimuli.

Which of the following statements is true about learning?

It occurs as the result of nervous system plasticity.

What are the three main anatomical differences between the parasympathetic and sympathetic nervous systems?

Sympathetic Parasympathetic Originate in the thoracic and lumbar regions of the spinal cord Originate in the hindbrain or in the sacral region of the spinal cord Ganglia are found in a chain that runs close to the spinal cord Ganglia are located close to the effector organ Single preganglionic neuron synapses with 10 or more postganglionic neurons Preganglionic neuron synapses with three or fewer postganglionic neurons

TRUE/FALSE: Brain size tends to increase with body size.

TRUE

TRUE/FALSE: Generally speaking, the vertebrate spinal nerves at the top of the spinal cord innervate upper parts of the body, and spinal nerves near the bottom of the spinal cord innervate lower parts of the body.

TRUE

TRUE/FALSE: Grouping neurons into ganglia permits more advanced integration.

TRUE

TRUE/FALSE: Habituation occurs based on changes that happen at the presynaptic terminal of the sensory neuron.

TRUE

TRUE/FALSE: One of the unique characteristics of the vertebrate nervous system is that it is encased within a cartilaginous or bony covering.

TRUE

TRUE/FALSE: The activity of a central pattern generator can be modified by sensory feedback.

TRUE

TRUE/FALSE: The autonomic ganglion is a relay station for autonomic neural pathways, and is also involved with neural integration.

TRUE

TRUE/FALSE: The hypothalamus contains a variety of regulatory centers to maintain homeostasis.

TRUE

TRUE/FALSE: The purpose of folding the surface of the cortex is to increase the capacity for neuronal connections.

TRUE

TRUE/FALSE: The sympathetic and parasympathetic systems are normally active simultaneously in a balanced way to maintain homeostasis.

TRUE

All vertebrate motor neurons release the neurotransmitter __________.

acetylcholine

In the sympathetic and parasympathetic nervous systems, the preganglionic neuron releases the neurotransmitter

acetylcholine.

In the vertebrate spinal cord, the dorsal horn is associated with __________ neurons, and the ventral horn is associated with __________ neurons.

afferent; efferent

In the vertebrate brain and spinal cord, white matter consists of __________ and gray matter consists of __________.

axons and myelin; cell bodies and dendrites

The vertebrate central nervous system is physiologically separated from the rest of the nervous system by the __________.

blood-brain barrier

In mammals, the midbrain can be grouped together with the pons and medulla oblongata, and is called the __________.

brainstem

In vertebrates, substances from the blood can access the central nervous system by

catalyzed transport.

Which of the following structures is NOT included in the limbic system?

cerebellum

The ventricles of the vertebrate brain contain

cerebrospinal fluid.

Split-brain syndrome follows from severing the __________.

corpus callosum

The mammalian cerebral hemispheres are connected by a mass of white matter called the __________.

corpus callosum

In vertebrates, the __________ nerves exit directly from the braincase.

cranial

The limbic system is associated with

emotion, motivation, decision-making. (all of the above)

Relative to other major groups of vertebrates, mammals and birds both have an enlarged

forebrain.

The hippocampus is important for the

formation of long-term memories.

NMDA and AMPA receptors both bind the neurotransmitter __________.

glutamate

In species with cortical folds, the outer regions of the folds are called __________ and the inner grooves are called __________.

gyri; sulci

The tendency to reduce the magnitude of a response following repeated stimulation is called __________.

habituation

In a newly discovered vertebrate, the area in the somatosensory cortex devoted to body part A is larger than the area devoted to body part B. This means that body part A

has more sensory neurons.

When preparing a mummy for burial, the ancient Egyptians and Greeks preserved this organ because it was believed to be the "seat of consciousness."

heart

Which structure is important for the formation of long-term memory in mammals?

hippocampus

Homeostasis is maintained by the

hypothalamus.

The basic mechanism for short-term sensitization begins with

increased presynaptic calcium.

Integrating centers typically contain large numbers of

interneurons.

The autonomic nervous system can be differentiated into three branches. Which of the following is NOT one of them?

limbic

The protective layer of connective tissue surrounding the brain and spinal cord is called the __________.

meninges (or singular meninx)

In most vertebrates, except the mammals, the __________ contains the regions that are involved in interpreting visual information.

midbrain

This brain structure is greatly reduced in mammals relative to other vertebrates.

midbrain

In nonmammalian vertebrates, the optic lobes are located in the

midbrain.

The simplest reflex arc, containing only a primary afferent and an effector neuron, is sometimes referred to as

monosynaptic.

The axons of afferent and efferent neurons are usually organized into structures called

nerves.

What receptors do the neurosecretory chromaffin cells of the adrenal medulla express?

nicotinic cholinergic

In the mammalian brain, the __________ lobe is involved with visual processing.

occipital

Functional magnetic resonance imaging works because brain areas that are working harder use more __________ than brain areas that are resting.

oxygen

The __________ nervous system is sometimes referred to as the "rest and digest" nervous system.

parasympathetic

Central pattern generators do NOT control

reflex arcs.

Among other things, the hindbrain is responsible for

regulation of involuntary behaviors such as breathing.

The three main regions of the vertebrate brain are the prosencephalon, the mesencephalon, and the __________.

rhombencephalon

An increase in a response following exposure to a strong or noxious stimulus is called __________.

sensitization

The only organ controlled by efferent motor neurons is __________.

skeletal muscle

Invertebrates possess a

solid ventral nerve cord.

The efferent branch of the peripheral nervous system is composed of the __________ and __________ divisions.

somatic motor; autonomic

The following structures of the mammalian nervous system, from posterior to anterior, are laid out in the following order:

spinal cord, medulla oblongata, pons, cerebellum.

The locomotor pattern generator is located in the

spinal cord.

The __________ nervous system is sometimes referred to as the "fight or flight" nervous system.

sympathetic

Hearing a loud and unexpected noise in the night activates the

sympathetic nervous system.

The __________ nervous system is most active during periods of stress or physical activity, while the __________ nervous system is most active during periods of rest.

sympathetic; parasympathetic

The __________ is essentially a relay station that filters sensory information and forwards it to the cortex.

thalamus

Most sympathetic pathways originate in the __________ regions of the CNS.

thoracic and lumbar

The somatosensory cortex and primary motor cortex are organized __________. That is, each part of the cortex corresponds to the specific part of the body that it governs.

topographically

The optic nerve functions to

transmit visual information from the retina.

List five ways that efferent motor pathways can be distinguished from autonomic pathways.

Efferent motor neurons control only one type of effector organ-skeletal muscle. Autonomic pathways control many organs. The cell bodies of motor neurons are located in the CNS, never in ganglia outside the CNS. Efferent motor pathways are monosynaptic, meaning that there is only a single synapse between the CNS and the skeletal muscle. This means that efferent motor neurons can be very long. Autonomic pathways are polysynaptic. Synapse morphology is different between autonomic and motor pathways. At the neuromuscular junction, a motor neuron splits into a cluster of axon terminals that branch out over the motor end plate. Autonomic neurons have several synaptic varicosities arranged in series like a string of beads. The size of the synaptic cleft is different. The synaptic cleft between the motor neuron and the muscle is much narrower than that between autonomic neurons and their effector cells. The nature of the neurotransmitter is different. All vertebrate motor neurons release acetylcholine at the neuromuscular junction, whereas sympathetic neurons release epinephrine and parasympathetic neurons release acetylcholine. The response of the effector organ differs. The effect of acetylcholine on skeletal muscle is always excitatory, whereas autonomic neurons may be excitatory or inhibitory.

TRUE/FALSE: Because cnidarians are not cephalized, they are incapable of complex behavior.

FALSE

TRUE/FALSE: Body organs are innervated by either the sympathetic nervous system or parasympathetic nervous system, but not both.

FALSE

TRUE/FALSE: Cranial nerves function solely to carry information from sensory neurons in the head, face, and neck to the brain.

FALSE

TRUE/FALSE: Invertebrates lack a brain, but instead have groupings of neurons called ganglia.

FALSE

TRUE/FALSE: Long-term potentiation is another term for sensitization.

FALSE

TRUE/FALSE: Phineas Gage was a railway worker who survived an accident in which a tamping iron was driven through his head. After recovery, his personality was changed based on damage to his medulla.

FALSE

TRUE/FALSE: Sensory feedback is required for the activity of a central pattern generator.

FALSE

TRUE/FALSE: The adrenal medulla is located in the hindbrain.

FALSE

TRUE/FALSE: The blood-brain barrier is completely impermeable.

FALSE

TRUE/FALSE: The brain is subdivided into several distinct regions. There is a great deal of integration within regions, but little integration between regions.

FALSE

TRUE/FALSE: The left and right cerebral hemispheres of mammals are functionally identical.

FALSE

TRUE/FALSE: The limbic system, sometimes referred to as the "emotional brain," is physically located in the hindbrain.

FALSE

TRUE/FALSE: The mechanism mediating LTP is the same as that mediating sensitization.

FALSE

TRUE/FALSE: The peripheral nervous system and the central nervous system tend to operate independently.

FALSE

TRUE/FALSE: The size of the cortex devoted to a particular body part generally reflects the physical size of that body part.

FALSE

TRUE/FALSE: The term "ganglion" is equivalent to the term "brain."

FALSE

TRUE/FALSE: Visual, auditory, touch, and olfactory signals are all routed through the midbrain and thalamus before processing at higher levels.

FALSE

In its protective role, the blood-brain barrier becomes an obstacle in delivering therapeutic drugs to specific regions of the brain in the treatment of a variety of brain disorders. Describe what the blood-brain barrier is made of, and how different compounds are capable of crossing it.

The blood brain barrier is formed by tight junctions between the endothelial cells lining the brain capillaries. It prevents materials from leaking out of the bloodstream and into the central nervous system. These cells do not perform pinocytosis. Despite the tight junctions, there are still ways that compounds can cross the blood-brain barrier, including: 1. Dissolving in the membrane. Small lipid-soluble molecules such as ethanol and some barbiturate drugs can cross directly into the central nervous system. 2. Catalyzed transport mechanisms (protein exchanger, channel, pump) allow the brain to take up circulating nutrients such as glucose and amino acids. 3. In some areas of the brain, the blood-brain barrier is more permeable. In particular, the regions around the pineal gland, the pituitary gland, and parts of the hypothalamus are quite permeable, allowing secreted molecules such as hormones to leave the brain and enter the circulatory system.

What four major brain structures are included in the limbic system? Where is it located in the vertebrate brain? What does the limbic system do?

The limbic system is part of the forebrain, and lies on the border between the cortex and the rest of the brain. The four main structure included in the limbic system are (1) the amygdala, (2) the hippocampus, (3) the hypothalamus, and (4) the olfactory bulbs. The limbic system is often called the "emotional brain" because it controls emotions such as pleasure and fear, as well as decision-making, motivation, sex drive, hunger, and memory. The hypothalamus, within the limbic system, is also responsible for regulation of homeostasis, including body temperature, fluid balance, blood pressure, and body weight.