Week 3 Summary - Brain and Behaviour PDF

WEEK 3: Biological aspects of Psychology 2 Week Objective 1: Identify and describe the functions of the peripheral and central nervous systems The peripheral nervous system has two components, each of which performs both sensory and motor functions. 1. The Somatic Nervous System. The somatic nervous...

WEEK 3: Biological aspects of Psychology 2 Week Objective 1: Identify and describe the functions of the peripheral and central nervous systems The peripheral nervous system has two components, each of which performs both sensory and motor functions. 1. The Somatic Nervous System. The somatic nervous system carries information from the senses to the CNS and sends movement instructions back to the muscles that move the skeleton. Sensory neurons bring information into the brain. Motor neurons carry information from the brain to direct motion. 1. The Autonomic Nervous System. The autonomic nervous system carries messages back and forth between the CNS and the body’s organs and glands. It has two divisions. The sympathetic nervous system mobilises the body for action through the fight-or-flight syndrome. The parasympathetic nervous system does the opposite: it slows organ and gland activity to conserve the body’s energy. The brain and the spinal cord together make up the central nervous system (CNS). The CNS is made up of groups of neuronal cell bodies called nuclei and the fibre tracts (or pathways) of axons that connect them. The Spinal Cord transmits information between the peripheral nervous system and the brain. It is made up of multiple segments that control sensation and movement in different parts of the body. • • • Reflexes are quick, involuntary muscular responses that are initiated on the basis of incoming sensory information that occur in the spinal cord without instruction from the brain. The brain is informed of each reflex after it occurs. The spinal cord is an example of a feedback system, a process in which information about an action’s results are conveyed back to the source of the action so that further adjustments to the activity can be made. In the spinal cord sensory neurons are afferent neurons and carry information toward the brain. Motor neurons are efferent neurons and carry information away from the brain. The Brain directs all psychological activity, maintains life functions and responds to stimuli. It consists of three distinct areas each of which has specific roles to play in brain function: • • the hindbrain the midbrain • the forebrain These are examined more closely under Weekly Objective Two. Weekly Objective 2: Describe basic brain anatomy The human brain directs all psychological activity, maintains life functions and responds to stimuli. It consists of three distinct areas, each of which has specific roles to play in brain function: 1. The hindbrain is located directly above the spinal cord and links it to the brain. The hindbrain consists of three areas: • medulla oblongata—controls the basic physiological functions such as heartbeat, circulation and respiration • The reticular formation is a network of cells running throughout the hindbrain and into the midbrain that alters the activity of other brain structures. It is involved in arousal and attention. The locus coeruleus, an area thought to be involved in directing attention, is activated by the reticular formation. • The cerebellum controls finely coordinated movements, stores well-rehearsed movements, and may also play a part in higher order cognitive processes, including speech. 1. The midbrain sits above the hindbrain and is surrounded by the forebrain. It consists of two structures: • tectum—involved in orienting to visual and auditory stimuli • tegmentum—involved in movement and arousal. The midbrain controls certain automatic behaviours that coordinate simple movements with sensory input. • The substantia nigra is a midbrain structure that, together with the striatum, is involved in smoothly initiating movement. • The midbrain and parts of the hindbrain other than the cerebellum are called the brainstem. 1. The forebrain is the largest and most sophisticated part of the brain. It is involved in complex sensory, emotional, cognitive and behavioural processes. The major components of the forebrain are as follows: • hypothalamus—regulates behaviours such as eating, sleeping, sexual activity and emotional experience. The suprachiasmatic nuclei, part of the hypothalamus, regulate an approximately 24-hour clock that determines biological rhythms. • thalamus—processes sensory information as it arrives and transmits it to higher brain centres. Plays an important role in processing and making sense out of sensory information. • cerebrum—includes the cerebral cortex (which is examined in the next section), as well as the following subcortical structures: • basal ganglia—involved in a wide range of functions, particularly movements and judgements requiring minimal conscious thought • limbic system - includes the hypothalamus, the septum and two structures that play important roles in regulating memory and emotion. • The amygdala is involved in fear and other emotions and may influence our sensitivity to other people. • The hippocampus is important in the formation of memories. The cerebral cortex is the outer surface of the cerebral hemispheres. It comprises 80 per cent of human brain mass, and is a 3 mm thick layer of densely-packed neurons that encloses the rest of the brain that performs sophisticated functions, including: • • the analysis of information from all the senses control of voluntary movements higher order thought • Other complex aspects of behaviour and mental processes. • The brain is divided into two hemispheres, each of which consists of four lobes: occipital, parietal, temporal and frontal. Each of these lobes has a number of specific, highly specialised functions. The lobes are used as the anatomical or physical landmarks for describing the cortex. The functional areas of the cortex include the sensory, motor, and association cortex. Sensory Cortex - Different regions of the sensory cortex (or sensory area) receive information from different senses. • Visual information is received by the visual cortex in the occipital lobe. • Auditory information is received by the auditory cortex in the temporal lobe. • Skin information about touch, pain and temperature is received in the somatosensory cortex in the parietal lobe. Information about skin sensations from neighbouring parts of the body comes to neighbouring parts of the somatosensory cortex. Motor Cortex Neurons in specific areas of the motor cortex in the frontal lobe create voluntary movements in specific parts of the body. Populations of neurons in many interconnected areas of the motor cortex work together to create desired movements. Association Cortex Parts of the cerebral cortex not directly involved with sensory information or movement are referred to as the association cortex. These areas perform complex cognitive tasks, receiving information from more than one sense or combining sensory and motor information. Damage to association areas can create deficits in all kinds of mental abilities. Aphasia is a deficit in understanding and producing language. • Damage to Broca’s area in the frontal lobe results in problems in organising speech called Broca’s aphasia. Victims have difficulty speaking and often produce grammatically incorrect language. • Damage to Wernicke’s area in the temporal lobe can leave a person able to speak but unable to understand the meaning of words or speak understandably. Many areas of the association cortex are related to language, depending on whether language is spoken or written, and whether particular grammatical and conceptual categories are involved. Weekly Objective 3: explain basic differences between the major brain imaging techniques There are several technological advances in the way we can study the brain: 1. The electroencephalograph (EEG) measures general electrical activity in the brain. 1. Positron emission tomography (PET) scan records where radioactive substances are concentrated as the brain performs various tasks. 1. Magnetic resonance imaging (MRI) exposes the brain to a magnetic field and measures the resulting radio frequency waves to produce a structural picture of the brain. 1. Functional magnetic resonance imaging (fMRI) uses a magnetic field to detect changes in blood flow and reflects ongoing changes in the activity of neurons. 1. Diffusion tensor imaging (DTI) is a variant on fMRI and traces activity of axon pathways. 1. Transcranial magnetic stimulation (TMS) temporarily disrupts the function of a part of the brain. TMS can be combined with MRI to refine localisation of brain activity. Weekly Objective 4: identify and describe the functions of the endocrine system The endocrine system, like the nervous system, influences a wide variety of behaviours. Endocrine organs or glands secrete chemicals called hormones, which travel via the bloodstream and affect coordinated systems of target organs that have receptors for them. Sex differences are partially due to hormonal differences but also depend on biological and social forces. The brain controls the secretion of hormones. The hypothalamus controls the pituitary gland which controls endocrine organs in the body. When the brain interprets a situation as threatening, the pituitary releases adrenocorticotropic hormone (ACTH), which causes the pituitary gland to release the hormone cortisol into the bloodstream, which acts on cells throughout the body, including the brain. One effect is activation of the sympathetic nervous system resulting in the fight-or-flight syndrome (also known as the fight-flight reaction), which prepares the body for action in response to danger or other stress. After the immediate threat is over, hormones provide feedback to the brain and secretion of ACTH and cortisol is terminated. This feedback and suppression arrangement is called a negative feedback system. The nervous system and the endocrine system – both systems of communication between and among cells – are integrated to form the biological basis for a smoothly functioning self that is filled with interacting thoughts, emotions, and memories and is capable of responding to life’s challenges and opportunities with purposeful and adaptive behaviour.