CHAPTER 2 Flashcards
Central Nervous System (CNS)
a major division of the nervous system comprising the brain and spinal cord, which receives sensory neural messages from and transmits motor neural messages to the PNS
Brain
a complex organ contained within the skull that coordinates mental processes and behaviour, and regulates bodily activity
Spinal cord
a cable of nerve tissue that extends from the brain, connecting it to the PNS and is composed of afferent and efferent tracts (SAME)
Afferent tracts
transmit sensory messages from the PNS to the brain (sensory = afferent)
Efferent tracts
transmit motor messages from the brain to the PNS (motor = efferent)
Peripheral Nervous System (PNS)
a major division of the nervous system comprising every neuron in the body outside the CNS, and transmits neural messages between the CNS and the body
Two subdivisions of the PNS
somatic and autonomic nervous systems
Somatic nervous system
a division of the PNS that transmits neural messages related to voluntary motor movement
What is the somatic nervous system comprised of?
sensory neural pathways and motor neural pathways
Skeletal muscles
muscles connected to the skeleton that carry out voluntary motor movements
Sensory receptors
nerve endings that detect sensations
Motor neural messages
travel from the CNS to skeletal muscles via efferent pathways
Sensory neural messages
travel from sensory receptors to the CNS via afferent pathways
Autonomic nervous system
a division of the PNS that regulates visceral muscles, organs, and glands, and transmits neural messages to the CNS about their activity
Visceral muscles, organs, and glands
muscles, organs, and glands not connected to the skeleton that are predominantly self-regulating and do not require conscious control
Two subdivisions of the autonomic nervous system
Sympathetic and parasympathetic nervous systems
Sympathetic nervous system
a division of the autonomic nervous system that activates visceral muscles, organs, and glands, preparing the body to respond to a threat or stressor
Parasympathetic nervous system
a division of the autonomic nervous system that maintains the optimal and balanced functioning of visceral muscles, organs, and glands
3 types of neurons
motor neurons, sensory neurons, interneurons
Motor neurons (efferent)
transmit neural messages about motor movement from the CNS to the PNS
Sensory neurons (afferent)
transmit neural messages about bodily sensations from the PNS to the CNS
Interneurons
transfer neural messages between sensory neurons and motor neurons and make up the entirety of the CNS
Dendrites
branched extensions of a neuron on which receptor sites are located
Receptor sites
protein molecules on the dendrites of a neuron that receive neurotransmitters
Soma
the cell body of a neuron, which contains the nucleus
Myelin sheath
insulates the neuron and prevents disturbance from other neurons
Axon
transmits electrical impulses from the cell body to the dendrites of other neurons
Axon terminal
the ends of a neuron that release neurotransmitters into the neural synapse
Conscious response
a deliberate and voluntary action that is initiated by the brain and performed intentionally by the body
5 steps to how the somatic nervous system and the central nervous system interact to enable conscious responses
- The sensory stimulus comes into contact with sensory receptors
- This sensory neural message is transmitted to the brain
- The brain processes this sensory information, coordinating and initiating a conscious motor response
- This motor neural message is transmitted via efferent pathways to skeletal muscles
- The skeletal muscles carry out the conscious motor response to the sensory stimulus
Sensory receptors
nerve endings that detect internal sensations in the body and external sensations from the environment
Unconscious response
an automatic and involuntary action that is performed by the body independently of the brain
8 unconscious physiological sympathetic responses
- Heart rate increases to increase blood flow
- Breathing rate increases and lung airways expand to increase oxygenation
- Pupils dilate to allow more light to enter the eyes
- Adrenal glands secrete stress hormones, such as adrenaline
- Sweat glands are activated
- Digestion is inhibited
- The bladder relaxes
- The body releases more glucose
8 unconscious physiological parasympathetic responses
- The heart beats at a regular rate
- Lung airways constrict to enable regular breathing rate
- Pupils constrict according to external light levels
- Adrenal glands do not secrete stress hormones
- Sweat glands are regulated
- Digestion occurs normally
- Urination is controlled
- The body releases less glucose
Spinal reflex
an unconscious response to sensory stimuli that is initiated by interneurons in the spinal cord independently of the brain
Why is the spinal reflex important?
it is a survival tool as it requires less processing than conscious responses because it is immediately initiated by the spinal cord in response to sensory stimuli, rather than consciously processed by the brain
4 steps of the spinal reflex
- A dangerous or harmful sensory stimulus is detected by sensory receptors, which transmit this sensory message via sensory neurons in the somatic nervous system to the spinal cord
- An interneuron in the spinal cord immediately relays this sensory neural signal from a sensory neuron to a motor neuron as a motor neural signal, initiating an automatic and unconscious motor response
- The motor message is transmitted via motor neurons in the somatic nervous system to skeletal muscles, which carry out this unconscious motor response to the dangerous or harmful sensory stimulus
- The sensory message continues to travel via afferent tracts in the spinal cord to the brain, which then independently registers the sensation that triggered the spinal reflex
