Unit 2: Nerve Impulses & Neural Communication Flashcards
two divisions of the nervous system
1) central nervous system (CNS)
2) peripheral nervous system (PNS)
role of central nervous system
- consists of the spinal cord and the brain
- receives and processes information from internal and external environment
- integrates this information to illicit appropriate responses in the body to maintain homeostasis
role of peripheral nervous system
- includes all neural tissue outside the CNS
- provides communication between the CNS and the rest of the body
- has two divisions: afferent and efferent neurons
role of afferent neurons
transmits sensory and visceral information from organs and sends it to the CNS
role of efferent neurons
transmit information from the CNS to the organs in the PNS
what are neurons?
cells that rapidly send and receive electrical signals
branches of the efferent division
- somatic nervous system = consist of motor neurons to help with movement
- autonomic nervous system = regulate function of internal organs
role of somatic nervous system (SNS)
- voluntary control of muscles
- innervate skeletal muscles (i.e leg)
role of autonomic nervous system (ANS)
- regulates involuntary visceral processes like heart rate, blood pressure, respiration, digestion
- innervate all other peripheral effectors (smooth muscle, cardiac muscle, glands, adipose tissue)
divisions of autonomic nervous system
1) parasympathetic = “rest and digest”
2) sympathetic = “fight or flight”
types of cells in the nervous system
1) neurons = excitable cells
2) glial cells = support cells
3 main parts of a neuron
1) cell body (soma) = contains the nucleus and most organelles
2) dendrites = receive incoming signals at synapses
3) axon = sends outgoing information
structure of a cell body
- contains a nucleus and other organelles
- essential to the well-being of the neuron
- the position varies in different type of neurons
structure of a dendrite
- thin, branched processes with smaller branches off them
- increase the surface area of the neuron
- allow communication with multiple other neurons
structure of an axon
- originates from an axon hillock of cell body
- varies in length
- transmit electrical signals (action potentials) from cell body to axon terminal
axon hillock
- where an axon originates
- where action potentials are initiated
axon terminal
- the region where neurotransmitters are released from after signal reaches it
- makes a synaptic contact with another cell
- contains mitochondria
what is an action potential?
- when a change in a membrane potential occurs, and the inside of the cell is positive compared to the outside
- allows information to be transmitted over long distances in axons
what is a synapse?
the site of communication between two neurons or between a neuron and an effector organ
–> axon terminal meets target cell
2 types of transportation in neurons
- anterograde transport = cell body to axon terminal
- retrograde transport = axon terminal to cell body
what is axonal transport?
- two types: (1) slow axonal transport and (2) fast axonal transport
- a mechanism for moving products between cell body and the axonal terminal of neurons
- slow axonal transport is used for small soluble molecules in cytosol
- fast axonal transport is used for movement of vesicles using microtubule tracks
two ways to classify neurons
1) structural classification
2) functional classification
structural classification of neurons
- based on the number of processes (axons and dendrites) that project from the cell body
- 4 classes: multipolar, bipolar, pseudounipolar, anaxonic
functional classification of neurons
- based on the direction of the information
- 3 classes: afferent, interneurons, efferent
structural characteristics of multipolar neurons
- many processes
- highly branched (5-7 dendrites) + 1 axon
- lack long extensions
- must abundant neuron
structural characteristics of bipolar neurons
- 2 approximately equal projections from cell body
- single axon + single dendrite that branch off the cell body
structural characteristics of pseudounipolar neurons
- cell body is attached to a single axon
- the dendrites are fused to the axon and appear as a single projection
- most abundant afferent neuron
structural characteristics of anaxonic neurons
- lacks an axon
- has numerous dendrites projecting from it
- functions has an interneuron in the CNS
what are interneurons and their role?
- intermediate neurons between sensory (afferent) and motor (efferent) neurons
- enables communication between sensory or motor neurons and the central nervous system
- has very complex branching (are anaxonic)
types of sensory (afferent) neurons
1) interoceptors
2) exteroceptors
3) proprioceptors
role of interoceptors
- monitor internal systems (digestive, respiratory, reproductive etc.)
- internal senses (taste, pain etc)
role of exteroreceptors
- monitor exernal environment
- external senses (touch, temperature, pressure etc.)
- distance senses (sight, smell, hearing)
role of proprioceptors
- relay information where our limbs are to allow for coordinated movements
- monitor position and movement of skeletal muscles and joints
role of glial cells
- provide strucural integrity to thte nervous system (“the glue”)
- preserve physical + biochemical structure for neurons to carry out function
- essential for survival and function of neurons
5 types of glial cells
- ependymal
- microglia
- astrocytes
- oligodendrocytes
- schwann cells
characteristics and role of ependymal cells
- highly branched processes that have cilia or micro cilia
- form the epithelium called ependyma
- they line the spinal cord and ventricles of the brain and contribute to the production of cerebrospinal fluid (CSF)
characteristics and role of microglia
- have many fine-branched processes (“thorny”) that monitor and protect neurons
- transform into phagocytic macrophages to internalize and destroy neuronal debris, waste products, pathogens in brain
characteristics and role of astrocytes
- large star-shaped cells with many projections
- participate in the blood-brain barrier to regulate what neurons are exposed to from the blood stream
- provides physical support (act as bars)
- highly metabolically active and provide substrates for ATP production
- repair damaged neural tissue
- control interstitial environment
characteristics and role of oligodendrocytes
- small cell bodies with few processes
- projections contact several axons of other neurons
- act to insulate axons by wrapping their cell processes tightly around them = form myelin sheath
characteristics and role of schwann cells
- insulate axons by forming myelin sheath
- many individual cells (not just one large piece)
- leave tiny unmyelinated gaps between cells called “nodes of Ranvier”
what is the blood brain barrier?
- is at the cellular level
- projections from astrocytes protect capillaries from allowing substances from entering
importance of myelin sheath
- rolled up plasma membrane surrounding axons
- form an insulating layer that prevents leakage of electrical current
- helps increase speed and efficiency of action potentials in an axon
internodes
myelinated segments of axons
nodes of ranvier
- gaps between internodes
- where axons may branch
- unmyelinated