Foundations of Biological Sciences 152 Quiz Chapter 31

True

True or False? The nervous system must be able to send signals to, and receive signals from, all parts of an animal’s body.

Excitable Cells

• in general its cell membrane can generate and conduct impulses, or action potential

  • permits neurons to carry signals over long distances

Neurons

• all parts of the animal nervous system are composed of _____

• Multi-part, typically elongate, cells that are bundled into long strands called nerves

• Thousands of _____ within a sheath

• originate in the central nervous system

• Signals are delivered to only defined locations

Nerves

• Neurons are multi-part cells that are bundled into long strands called ______

• An individual ____ will consist of thousands of individual neurons bundled together in a sheath

• Originate in the central nervous system which consists of the brain and spinal cord

Sheath

• multiple neurons bundled into a nerve _____

Four anatomical regions of a Neuron

1) A set of Dendrites

2) A Cell body

3) An axon

4) A set of presynaptic axon terminals

Dendrites

receive signals from other cells

Cell body of a neuron

• contains the nucleus and organelles and serves to integrate the incoming signals

Axon

a long process that is anatomically specialized for long-distance signal conduction

Synapse

• the point of innervation which allows the nervous system to communicate with and control other cells

• cell to cell contact point that is specialized for signal transmission from one cell to another

Glial Cells

• found in the vertebrate nervous system

• While these cells are not excitable and do not transmit impulses, they are nonetheless important cells that support, insulate and nourish

• Central nervous system relies upon these for metabolic functions

Myelin

• glia wrap around the axons to form an electrical insulation

• helps to improve the efficiency and speed of transmission

The Central Nervous System

• brain and spinal cord

The peripheral Nervous system

• all parts of the nervous system except brain and spinal cord

False; Neurons must be excitable

True or False? neurons do not need to be excitable.

Action potential

• are temporary, transient, reversals of electrical potentials on either side of the membrane

• a state of reversed polarity of the cell membrane where an ______ present

  • permits neurons to carry signals over long distances

Electrical Potential

neurons establish an _____ by using ion channels n their membranes to maintain a net positive charge outside of the cell, and a net negative inside

Non polar lipids

the membrane, because it is composed of ________, is a crucial component in establishing these action and electrical potentials

Voltage

If left uninterrupted in a bulk solution, positive and negative ions would simply be attract to each other. A physical barrier allows the charges to be seperated, establishing a ______

Membrane Potential

a potential difference (voltage) across a membrane is called __________

Ion Concentrations

Changes in _______ across the membrane are mediated by ion channels.

False; The most important ion channel is the sodium - potassium pump

True or False? The most important ion channel is the saline pump.

The resting potential

of a neuron is primarily a function of the concentrations of sodium and potassium ions on either side of the membrane.

Sodium - Potassium Pump

To move the ions, the _________ uses one molecule of ATP to pump three sodium ions into the cell and two potassium ions out

Potassium Leak Channels

Potassium is allowed to move somewhat freely through _______

Potassium

will either follow a concentration gradient and move out of the cell, or will be pulled back into the cell by the electrical gradient

True

True or False? Due to strong voltage gradient across the membrane, and only because the ions closest to the membrane are affected, only very small changes in the distribution of ions are needed to propagate an action potential

Gated

some ion channels are _____, they will only open and close in response to a particular stimulus

Voltage - Gated Channels

respond to a change in membrane potential

Stretch - Gated Channels

respond to a physical stimulus, like touch pressure

Ligand - Gated Channels

will only open when their activator molecule binds to them

Depolarization

• occurs when the inside of a cell becomes less negative than it is at rest

• when gated channels are active

Hyperpolarization

• occurs when the inside of a cell becomes more negative

• when gated channels are active

Invertebrates

tend to use large-diameter neurons to quickly propagate actions potentials.

Squids

have. the largest - diameter neurons in the animal kingdom

Vertebrates

used saltatory conduction

Saltatory Conduction

use the gaps between myelin sheaths to increase the speed with which a potential is propagated

Chemical Synapse

when the action potential reaches the presynaptic bump, a chemical called a neurotransmitter is released. The neurotransmitter crosses a small gap, the synaptic cleft, before reaching the next cell. Neurotransmitter causes the electrical potential to be transmitted to the postsynaptic cell.

Electrical Synapse

the presynaptic cells share cytoplasm through gap junctions. The potential propagates very quickly though this

An Example of a Chemical Synapse

a synapse between a neuron and a muscle cell

True

True or False? sometimes, individual potentials are too small on their own to propagate a potential, but several potentials can be summed by a neuron in order to produce a single strong enough to cross the threshold for synaptic transmission.

Sensory Receptor Cells

are cells specialized for receiving energy from certain stimuli - light, pressure, chemical - and converting that energy into an action potential also know as signal transduction

Sensory receptor proteins

• sensory receptor cells depends upon them

• detect the stimulus and either directly or indirectly trigger a change in membrane potential

Ionotropic receptors

can directly trigger a membrane potential when they detect a stimulus

Metabotropic receptors

1) adorant molecule binds to the receptor

2) activate a G-protein

3) G-protein activates an enzyme that causes an increase in a secondary messenger

4) secondary messenger opens ion channel

Mechanoreceptors

• respond to mechanical distortion of the cell membrane; most are ionotropic

  • cold and hot receptors

  • light touch, deep pressure

  • Pain = free nerve endings

Stretch Receptors

• muscles adjusts the muscles strength of contraction to match the load the muscle can sustain

• Receptors in the muscle detect how much the muscle is being lengthened by the load; keep the muscle as stable as the load increases

Chemoreceptors

senses olfaction and gustation (smell and taste)

Olfaction

sense of smell

Dogs

• have 220,000,000 olfactory receptors

• specialized ‘vomeronasal’ organ

Humans

• have about 5 million olfactory receptors

Male Moths

have thousands of receptors on their antennae that respond to pheromones emitted by the females

Auditory Systems

use mechanoreceptors to sense sound pressure waves, many hearing organs have a membrane that move in and out when sound pressure waves hit us. In mammals this is the tympanic membrane

Tympanic Membrane

ear drum

The Ear

hearing and equilibrium

Cochlea

• hearing

• hold fluid in the _______ duct

• Equilibrium: vestibule, semicircular canals

Visible light spectrum

750-400nm

Vertebrate Eyes

• Image forming eyes, like a camera

• Focusing and image formation by cornea and lens on retina

Photoreceptors

• receptor cells sensitive to light

• are metabotropic

• consist of cones and rods

Rhodosins

• consist of the protein opsin and a light - absorbing group 11-cis-retinal… changes to trans when exposed to light

Cones

• color vision

• better acuity

• need bright light

• 5 million

• have better visual acuity

• fewer per nerve fiber

Rod

• less visual activity

• better in low light

• 100 million

• _____ have less visual acuity

• many _____ per nerve fiber means less ability to discriminate

Compound Eyes

• arthropods have them consisting of units called ommatidia

• each ommatidium points in a slightly different direction, the higher the image resolution

• Fast-flying predators such as dragonflies have up to 30,000

Ommatidia

• each has a lens to focus light onto photoreceptor cells containing rhodopsin

Ultraviolet Vision

Birds and insects see ____,photoreceptors in ultraviolet range <400nm

Sponges

do not have a nervous system

The Cnidarians and Echinoderms

have nerve nets, the simplest type of nervous system

Centralization

integrating neurons became clustered together in centralized organs (e.g. brain and spinal cord)

Cephalization

major integrating areas became concentrated toward the anterior end of the animal (head)

Centralization and Cephalization

Evolution of nervous system followed two major trends

Vertebrate Brains

have three main regions; forebrain, midbrain and hindbrain

Medulla oblongata

• how the brain and spinal cord are connected

• most posterior part of the hindbrain

Sensory Functions of the Nervous System

• internal conditions and external environment

Integrative Functions of the Nervous System

relays sensory information to effectors

Motor Functions of the Nervous System

• reacts to sensory / integrative input

• carry signals to muscle cells, stimulating contraction

Grey matter

• the outer 5mm of ______ in the cerebrum is responsible for consciousness, thought and abstraction

Sympathetic Nervous System

fight or flight

Parasympathetic Nervous System

rest and digest

Sensory Neurons

carry signals from sense organs to central nervous system

Spinal Nerves

arise in pairs, one going to each side of the body

Presynaptic Cell

cell that conducts signals into the synapse

Postsynaptic cell

the cell that conducts signals away from the synapse

Presynaptic axon terminal

at its end, an axon branches, and each branch terminates in a small swelling called…

Resting Potential

the membrane potential of a resting neuron is referred to as the ________