Division of the Nervous System: Flashcards
Peripheral nervous system:
consists of the 31 pairs of spinal nerves, which carry sensory and motor pathways of the somatic nervous system, and motor pathways of the autonomic nervous system; connects the CNS with the body and with the outside world
Somatic nervous system:
part of the PNS, the SNS is made up of sensory pathways from the sensory receptors on the body surface, and motor pathways controlling skeletal muscle; maintains communication between the CNS and the outside world
Autonomic nervous system:
part of the PNS, the ANS is made up of motor pathways controlling the activity of internal body systems such as the heart and circulatory system, the intestines, and various glands; it has two branches, the sympathetic and the parasympathetic
Divisions of the nervous system:
-the nervous systems consists of billions of neurons and is highly organised
-the brain is the key processor of information but relies on sensory input from receptors like eyes, ears, and skin to connect with the external world
-sensory pathways carry this input to the brain via the spinal cord, except for vision and hearing, which connect directly to the brain
-the brain also control movement and internal systems like the heart and digestive system through motor pathways
-these pathways are made up of motor neurons, while sensory neurons handle incoming signals, relay neurons, or interneurons connect different parts of the CNS and form the majority of neurons in the brain
-the CNS includes the brain and spinal cord, while the PNS consist of spinal nerves that link the CNS to the rest of the body
-together, they manage sensory input and motor responses
Hindbrain and Midbrain:
-the hindbrain is made up of the medulla, pons and cerbellum a.k.a the brainstem
-the brainstem is essentially a continuation of the spinal cord within the brain, with sensory and motor pathways carrying information to an from higher brain centres
-also buried in within the brainstem is the ascending reticular formation, a network of neurons vital to sleep and arousal functions of the brain
-the brainstem also contains major autonomic centres; autonomic pathways travel down from these centres through the spinal cord and are distributed throughout the body by the spinal nerves
-the cerbellum is a large structure located on the back surface of the brain stem
-its major functions relate to the control of movement, and damage results in a loss of motor coordination
Forebrain: diencephalon
-this is the largest division of the brain, and is subdivided into two major components, the diencephalon and the telencephalon (also known as the cerebral hemispheres or cerebrum)
Diencephalon:
-this subdivision of the forebrain contains two main structures, the thalamus and hypothalamus
-the thalamus is an important sensory structure, relaying sensory information from pathways ascending up through the spinal cord and the brainstem on to the cortex
-the hypothalamus lies at the base of the brain, through its control over the putuitary gland, which lies just below it, and the autonomic centres in the brainstem, the hypothalamus is involved in many of the body’s physiological functions
Forebrain: telencephalon or cerebral hemispheres
-the cerebral hemispheres contain the systems and structures of most interest to psychologists
-high-level cognitive and emotional processes are controlled from these areas, although it must be remembered that all parts of the brain are heavily interconnected, especially the subsystems of the hemispheres
-three major systems make up the cerebral hemispheres: the limbic system, the basal ganglia, and the cerebral cortex
limbic system, basal ganglia + cerebral cortex
-limbic system: this consists of a set of interconnected structures, including the hippocampus, amygdala, septum, and cingulate + they are involved in functions such as learning, memory, and especially emotions
-basal ganglia: the basal ganglia have important functions in relation to movement and motor control, they include the caudate nucleus, the putamen, and the globus pallidus + damage to the basal ganglia results in movement disorders such as Parkinson’s disease
-cerebral cortex: this is the most recently evolved part of the brain, and the amount of cortex distinguishes humans from other species + it contains within it the highest cognitive functions, such as planning and problem-solving, languagem consciousness, and personality, as welll as perception and control of movement
Peripheral nervous system (PNS):
-the PNS is made up for the 31 spinal nerves
-these contain millions of sensory (afferent) and motor (efferent) pathways allowing the brain to be aware of what is going on in the body and outside worlds, and to control our various response systems
-although highly complicated, the millions of pthaways making up the spinal nerves can conveniently be divided into the somatic and autonomic nervous systems
PNS: the somatic nervous system- first component
-the SNS is made up of two components:
-the first is made up of sensory or afferent pathways from the sensory receptors of the body - touch, pain, pressure, temperature
-these systems have specialised sensory receptors in the skin that respond to various stimuli by trigerring action potentials (nerve impulses) in sensory neurons
-these neurons carry the sesnory information into the spinal cord via the spinal nerves
-in the spinal cord they make synaptic connections onto neurons that carry the information up the spinal cord to the brain, where it is processed
PNS: the somatic nervous system-second component
-the second component is made up of motor or efferent pathways
-the axons of motor neurons travel in spinal nerves out to the skeletal muscles of the body, allowing the brain to control bodily movement
-commands to move our muscles are formulated in the cerebral cortex of the forebrain, and then travel down through the brain and spinal cord to the spinal nerves
-we can see the two components of the SNS as integrating the brain with the outside world, sensory pathways carry information from the environemtal stimuli, but we also have an internal environment to regulate, and for this we have another division of the spinal nerves
PNS: the autonomic nervous system
-the ANS plays a central role in states of bodily arousal
-ANS centres are located in the brainstem
-from here, ANS pathways run down through the spinal cord and are distributed throughout the body by the spinal nerves
-the ANS is concerned with the regulation of our internal environment, controlling vital functions such as body temperature, heart rate, and blood pressure
-the ANS is central to homeostasis, the maintenance of a constant internal environment, e.g. the way we keep a constant body temperature
-without homeostasis, snakes and other reptiles, for example, become inactive in the cold and spend as much time as they can in the sunshine to increase their body temperature, homeostasis allows an animal to become independent of the environment
-the ANS is vital to homeostasis as it constantly monitors and controls the internal environemnt
PNS: the ANS -two branches
-to carry out its functions, the ANS has two separate branches, the sympathetic and the parasympathetic
-nerve fibres from both branches connect with internal structures such as various glands, the heart and circulatory system, and the digestive system
-sympathetic arousal or dominance leads to a pattern of bodily arousal, with increases in heart rate and blood pressure and a decrease in activity in the digestive system
-parasympathetic dominance leads to the opposite pattern, one of the physiology calm, with lower heart rate and blood pressure and increased digestive activity
PNS: ANS- sympathetic arousal
-usually the two branches are in balance, but under certain circumstances the balance shifts and one branch becomes dominant
-these shift are determined by the body’s physiological requirements
-physical exercise need energy, and this is provided by sympathetic arousal
-similarly, if a dangerous or threatnening situation is perceived, higher brain centres signal the hypothalamus, a key structure buried deep in the brain to activate the sympathetic branch of the ANS
-this provides energy in case we need to respond physically to the situation, therefore, sympathetic arousal is an important part of the body’s response to stress- the fight or flight response
