Chapter 40: The Nervous System

Nervous System evolution

Species-specific ability to integrate information.

Increase in the size and complexity of the human brain leads to

Increased cognitive and mental ability.

Neural circuit motifs

Feedforward excitation, Feedback excitation, Feedback inhibition.

Invasive techniques for investigating nervous system function

Using fine-tipped microelectrodes to record action potentials; Electric current can be passed through microelectrodes to simulate stroke.

The use of microelectrodes to record action potential activity provides a single cell analysis that

Produces a topographic map, giving specific insight into the type of stimulus to which the neuron is “tuned

Single-unit analysis

Measures a sensory neuron’s receptive field.

Non-invasive techniques

fMRI – functional magnetic resonance imaging.

fMRI relies on

Hemoglobin in blood distorts the magnetic resonance properties of hydrogen nuclei.

PET scan

Uses radioactive tracers attached to glucose injected into the bloodstream.

Why is PET less commonly used?

Because of exposure to radioactive material.

Nerve nets

A simple, decentralized (no brain or spinal cord) nervous system found in certain invertebrates, such as jellyfish and sea anemone (cnidarians)

Nerve ring

A circular or horseshoe-shaped structure formed by a collection of nerve cells that surrounds the pharynx or esophagus in certain invertebrate animals (Ex. echinoderms (sea stars))

Ganglion pair + longitudinal nerve cord

a characteristic feature consisting of a chain of paired ganglia (or fused ganglia) along the body's midline, connected by longitudinal nerve cords. (Ex. Planarians (Dugesia))

Dorsal ganglia + ventral ganglia + ganglion pairs in body segments

Common in Arthropods.

Lobed brain + ganglia associated with internal organs

Cephalopods like octopus (largest invertebrate brain).

Central nervous system (CNS)

brain and spinal cord.

Peripheral nervous system

All nervous tissue outside of the CNS.

Pairs of cranial nerves

Pairs of spinal nerves

Afferent division

sensory.

Integration center

CNS.

Efferent division

motor.

Somatic nervous system

skeletal muscles (voluntary).

Autonomic nervous system

Visceral motor (involuntary) – smooth muscles, cardiac muscles, glands.

Sympathetic division

fight or flight responses.

Parasympathetic division

rest and digest.

Prosencephalon

Forebrain.

Mesencephalon

midbrain.

Rhombencephalon

Hindbrain.

Telencephalon

Cerebrum.

Diencephalon

Thalamus, Hypothalamus.

Metencephalon

Pons, cerebellum.

Myelencephalon

Medulla oblongata.

Major brain regions

Cerebrum, Cerebellum, Diencephalon, Brain stem.

Gray matter regions

nerve cell bodies and dendrites.

White matter regions

myelinated axons.

Cerebrum

the largest part of the brain.

Surface area of the brain is increased by

convolutions or folding.

Gyri (plu.); gyrus (sing.)

raised regions.

Sulci (plu.); sulcus (sing.)

shallow grooves.

Fissures

deeper grooves; Longitudinal fissure; Lateral fissure.

The lobes of the cerebrum

Frontal, parietal, temporal, and occipital lobes.

Frontal lobe functions

Abstract and conscious thoughts, declarative and explicit memory, mood, motivation, decision making, planning, speech production, judgement of behavior, voluntary motor control.

Parietal lobe functions

somatosensory processing, visuospatial processing, navigation.

Temporal lobe functions

Hearing, olfaction, grammar and vocabulary, forming long term memory.

Occipital lobe functions

Visual center.

Basal nuclei functions

subconscious adjustment and refinement of voluntary motor commands.

The limbic system

Emotional brain.

Amygdala

negative emotions such as fear, anxiety, aggression.

The brainstem

Midbrain, pons, medulla oblongata.

Midbrain

processes visual and auditory information.

Spinal cord

Relay signals from the PNS to the brain and vice versa.

Dorsal gray matter

integrates sensory inputs.

Ventral gray matter

contains motor neurons.

Components of the reflex arc

Sensory receptor – afferent sensory neuron – inter neurons – efferent motor neuron – effector.

Patellar tendon reflex

example for a monosynaptic reflex.

1. Tapping of the patellar tendon with hammer
2. Tapping of tendon causes quadriceps to stretch
3. Muscle spindle organs in quad detect stretch and generate action potential
4. Action Potential is carried by sensory neurons through the dorsal root to the spinal cord
5. Afferent neurons interact directly with a motor neuron in the ventral gray matter
6. The motor neuron is activated and carries the motor impulse or efferent signal back to the quadriceps muscl
7. The motor impulse causes the quadriceps muscle to contract, resulting in the extension of the leg or a gentle "jerk”

Human consciousness is measured using

electroencephalogram or EEG.

Alfa waves

Produced during resting with eyes closed.

Beta waves

fully awake and alert.

Cerebellum function

allowing you to do repeated work.

Arbor Vitae

The pattern of white matter in the cerebellum.

Lesions in Broca's area affect

Speech production.

Lesions in Wernicke's area affect

Language comprehension.

Spinal cord location

Vertebral cavity.

What is the primary purpose of feedback inhibition in neural circuits?

To prevent overexcitation. Done by excitatory neurons activating inhibitory neurons, which in turn inhibit the excitatory neuron

What is unique about the arthropod nervous system compared to other invertebrates?

Arthropods (e.g., insects) have a head region that contains a brain consisting of Dorsal and ventral ganglia pairs & Major sensory structures (e.g., eyes, antennae).

Ganglia are collections of nerve cell bodies located in the peripheral nervous system. True or False?

True.

What are cell bodies called outside the CNS?

Ganglia.

What sensory system in the human body is an example of feedforward excitation?

In the vision system.

Split into Left hemisphere, right hemisphere

Cerebrum, cerebellum, medulla.

What is the function of the blood-brain BBB?

To protect the brain from harmful substances and pathogens.

Which lobe is responsible for processing auditory information?

Temporal lobe.

What is responsible for the immediate reflexive responses to a loud unexpected noise?

Midbrain.

Region A:

Cerebral cortex grey matter.

Region B:

Cerebral cortex white matter.

Structure C:

Thalamus.

Structure D:

Ventricles.

Name an effect of damage to the Wernicke’s Area

difficulty in comprehending language.

When an individual is fully awake, the EEG records a pattern of

rapid, irregular beta waves.

With mind at rest and eyes closed, the EEG records

slower and more regular alpha waves.

As drowsiness and light sleep come on, the EEG records

theta waves.

In deep sleep, the EEG shows

even slower delta waves.

Neural Circuits

integrate sensory information and formulate appropriate motor responses.

Feedforward Excitation

The most common form of neural circuit. One presynaptic neuron whose neurotransmitter excites a postsynaptic neuron.

Feedback excitation

Excitatory neurons in a feedforward excitation circuit project back to neurons at earlier steps in neural pathways

Feedback inhibition

prevents the neural circuits from getting overexcited.

Investigating Neural Integration

Record neuronal activity. Block or stimulate activity in specific brain regions. Trace the axonal connections between one brain region and others.

Blood-brain barrier

Prevents most substances in blood from entering the cerebrospinal fluid.

The hypothalamus regulates

basic homeostatic functions of the body, both consciously and unconsciously.

Limbic System functions

Establishing emotional states.

Brain Stem

Connects the spinal cord with the rest of the brain.

The Spinal Cord

relays information from the PNS to the CNS.

Thalamus

the traffic roundabout. Receives sensory information from all parts of the body and relays it to the appropriate areas of the cerebral cortex for processing

The brain is protected by

Three layers of connective tissue, the meninges.

The three layers of meninges are

dura mater, arachnoid mater, pia mater.

Cerebrospinal fluid function

cushions the brain and spinal cord against physical shock and provides nourishment.

The brain's primary energy source is

glucose.

The sympathetic nervous system is also known as

fight or flight system.

The parasympathetic nervous system is also known as

resting and digesting system.

The cerebrum is divided into two

hemispheres, the right and left cerebral hemispheres.